Deputy Assistant Secretary of Defense Laura Cooper, the Pentagon official in charge of Ukraine and Russia policy, arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 23, 2019.

David Hale, Under Secretary of State for Political Affairs, arrives for a closed-door deposition as part of the impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 6, 2019.

Congressman Mark Meadows (R-NC) looks back at reporters as he enters a secure area as Deputy Assistant Secretary of Defense Laura Cooper testifies in a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Donald Trump on Capitol Hill in Washington, U.S., October 23, 2019.

Acting U.S. ambassador to Ukraine Bill Taylor arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 22, 2019.

Fiona Hill, former senior director for European and Russian affairs on the National Security Council, leaves after reviewing her previous testimony in the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 4, 2019.

U.S. foreign service officer Catherine Croft, who once served as a deputy to then-Special Envoy for Ukraine Kurt Volker, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 30, 2019.

Deputy Assistant Secretary of Defense Laura Cooper, the Pentagon official in charge of Ukraine and Russia policy, arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 23, 2019.

Timothy Morrison, special assistant to the president and senior director for Europe and Russia at the National Security Council, arrives for a closed-door deposition as part of the impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 31, 2019.

David Hale, Under Secretary of State for Political Affairs, arrives for a closed-door deposition as part of the impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 6, 2019.

Former U.S. ambassador to Ukraine Marie Yovanovitch departs after testifying in the U.S. House of Representatives impeachment inquiry into U.S. President Trump on Capitol Hill in Washington, U.S., October 11, 2019.

U.S. House Republicans speak to reporters after Deputy Assistant Secretary of Defense Laura Cooper arrived to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S. October 23, 2019.

Philip Reeker, U.S. acting assistant secretary of state for European and Eurasian Affairs, arrives to testify in impeachment inquiry against U.S. President Donald Trump, in Washington, U.S., October 26, 2019.

U.S. Ambassador to the European Union Gordon Sondland arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 28, 2019.

Kurt Volker, U.S. President Donald Trump's former envoy to Ukraine, arrives to be interviewed by staff for three House of Representatives committees as part of the impeachment inquiry into the president's dealings with Ukraine, at the U.S. Capitol in Washington, U.S. October 3, 2019.

Kurt Volker, U.S. President Donald Trump's former envoy to Ukraine, arrives to be interviewed by staff for three House of Representatives committees as part of the impeachment inquiry into the president's dealings with Ukraine, at the U.S. Capitol in Washington, U.S. October 3, 2019.

Acting U.S. ambassador to Ukraine Bill Taylor is pursued by members of the media as he arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 22, 2019.

Lt. Col. Alexander Vindman, director for European Affairs at the National Security Council, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 29, 2019.

U.S. foreign service officer Catherine Croft, who once served as a deputy to then-Special Envoy for Ukraine Kurt Volker, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 30, 2019.

Deputy Assistant Secretary of Defense Laura Cooper, the Pentagon official in charge of Ukraine and Russia policy, arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 23, 2019.

Christopher Anderson, who once served as a deputy to then Special Envoy for Ukraine Kurt Volker, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 30, 2019.

Congressman Mark Meadows (R-NC) looks back at reporters as he enters a secure area as Deputy Assistant Secretary of Defense Laura Cooper testifies in a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Donald Trump on Capitol Hill in Washington, U.S., October 23, 2019.

Fiona Hill, former senior director for European and Russian affairs on the National Security Council, departs after testifying in the U.S. House of Representatives impeachment inquiry into U.S. President Trump on Capitol Hill in Washington, U.S., October 14, 2019.

Acting U.S. ambassador to Ukraine Bill Taylor arrives on Capitol Hill before a closed-door hearing with members of Congress in Washington, U.S., October 22, 2019.

House Minority Whip Steve Scalise (R-LA) with other Republican congressmen speaks to the media outside a secure area as Deputy Assistant Secretary of Defense Laura Cooper testifies in a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Donald Trump on Capitol Hill in Washington, U.S., October 23, 2019.

U.S. Ambassador to the European Union Gordon Sondland departs after testifying at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 28, 2019.

A draft of a U.S. House of Representatives resolution formally laying out the next steps in the Democratic impeachment inquiry of President Donald Trump, authorizing public committee hearings and the public release of transcripts of closed-door depositions, is seen after its release on Capitol Hill in Washington, October 29, 2019.

Fiona Hill, former senior director for European and Russian affairs on the National Security Council, arrives to review her previous testimony in the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 4, 2019.

Timothy Morrison, special assistant to the president and senior director for Europe and Russia at the National Security Council, returns to testify at a closed-door deposition as part of the impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 6, 2019.

Timothy Morrison, special assistant to the President and senior director for Europe and Russia at the National Security Council, arrives on Capitol Hill to testify in private before members of congress, in Washington, U.S., October 31, 2019.

U.S. foreign service officer Catherine Croft, who once served as a deputy to then-Special Envoy for Ukraine Kurt Volker, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 30, 2019. REUTERS/Siphiwe Sibeko - RC1ECF8E2B90

Lt. Col. Alexander Vindman, director for European Affairs at the National Security Council, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 29, 2019.

Former U.S. ambassador to Ukraine Marie Yovanovitch arrives to testify in the U.S. House of Representatives impeachment inquiry into U.S. President Trump on Capitol Hill in Washington, U.S., October 11, 2019.

Lt. Col. Alexander Vindman, director for European Affairs at the National Security Council, arrives to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 29, 2019.

David Hale, Under Secretary of State for Political Affairs, arrives for a closed-door deposition as part of the impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., November 6, 2019.

Deputy Assistant Secretary of Defense Laura Cooper, the Pentagon official in charge of Ukraine and Russia policy, arrives to testify at a closed-door deposition as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump led by the House Intelligence, House Foreign Affairs and House Oversight and Reform Committees on Capitol Hill in Washington, U.S., October 23, 2019.

Acting U.S. ambassador to Ukraine Bill Taylor arrives on Capitol Hill before a closed-door hearing with members of Congress in Washington, U.S., October 22, 2019.