U.S. soldiers participate in the Eager Lion military exercise at the Jordan-Saudi Arabia border, south of Amman May 17, 2017.

Jordanian soldiers participate in the Eager Lion military exercise at the Jordan-Saudi Arabia border, south of Amman May 17, 2017.

U.S. and Jordanian soldiers participate in the Eager Lion military exercise at the Jordan-Saudi Arabia border, south of Amman May 17, 2017.

U.S. soldiers participate in the Eager Lion military exercise at the Jordan-Saudi Arabia border, south of Amman May 17, 2017.

Jordanian soldiers watch as smoke rises during Eager Lion military exercises at the Jordan-Saudi Arabia border, south of Amman May 17, 2017.

Tanks advance during Eager Lion military exercises near the Jordan-Saudi Arabia border, south of Amman May 17, 2017.

Image for illustrative purpose. U.S. soldiers participate in the Eager Lion military exercise at the Jordan-Saudi Arabia border, south of Amman May 17, 2017.

U.S. soldiers participate in the Eager Lion military exercises at the Jordan-Saudi Arabia border, south of Amman May 17, 2017.

U.S. and Italian soldiers participate in the Eager Lion military exercise at the Jordan-Saudi Arabia border, south of Amman May 17, 2017.

U.S. and Jordanian soldiers participate in the Eager Lion military exercise at the Jordan-Saudi Arabia border, south of Amman May 17, 2017.

U.S. soldiers participate in the Eager Lion military exercise at the Jordan-Saudi Arabia border, south of Amman May 17, 2017. Reuters: / Muhammad Hamed

U.S. soldiers participate in the Eager Lion military exercise at the Jordan-Saudi Arabia border, south of Amman May 17, 2017.

Tanks advance during the Eager Lion military exercise at the Jordan-Saudi Arabia border, south of Amman May 17, 2017.

A helicopter is seen next to the Jordanian flag during the Eager Lion military exercise at the Jordan-Saudi Arabia border, south of Amman May 17, 2017.