Special Counsel Robert Mueller arrives at his office in Washington, U.S., April 17, 2019. REUTERS/Joshua Roberts

Election officials wearing superhero costumes prepare ballots at a polling station during elections in Surabaya, East Java province, Indonesia, April 17, 2019 in this photo taken by Antara Foto.

A member of Azov battalion which is part of National Guard of Ukraine, nom de guerre Takho, is seen at a position on the front line near the city of Novoluhanske in Donetsk region, Ukraine April 12, 2019. Picture taken April 12, 2019.

A gaucho rides an untamed horse during Creole week celebrations in Montevideo, Uruguay April 17, 2019.

The Northrop Grumman Antares rocket, with Cygnus resupply spacecraft onboard, launches from Pad-0A, at NASA's Wallops Flight Facility in Virginia, U.S., April 17, 2019.

Climate activist Swedish teenager Greta Thunberg meets Pope Francis during the weekly audience at Saint Peter's Square at the Vatican, April 17, 2019.

A visitor jumps to pose for a photo behind a display at the the Unko ("poop" in Japanese) museum in Yokohama, Japan, April 17, 2019.

A man on a boat collects plastic materials from dirty water in Dhaka, Bangladesh, April 17, 2019.

A bunch of roses placed near Notre-Dame Cathedral is pictured at sunrise after a massive fire devastated large parts of the gothic structure in Paris, France, April 17, 2019.

Mwamini Kahindo, an Ebola survivor working as a caregiver to babies who are confirmed Ebola cases, holds an infant outside the red zone at the Ebola treatment centre in Butembo, Democratic Republic of Congo, March 25, 2019. Picture taken March 25, 2019.

A migrant from Central America talks with his famiy by a river during a break in his journey towards the United States, in Huixtla, Mexico April 16, 2019.

U.S. President Donald Trump speaks during an "Opportunity Zone" conference with state, local, tribal, and community leaders at the White House in Washington, U.S., April 17, 2019. REUTERS/Carlos Barria

Soccer Football - Champions League Quarter Final Second Leg - Manchester City v Tottenham Hotspur - Etihad Stadium, Manchester, Britain - April 17, 2019 Tottenham manager Mauricio Pochettino, Tottenham's Fernando Llorente and Son Heung-min celebrate after the match

Supporters of Peru's former President Alan Garcia react after the announcement that Garcia died in a hospital after shooting himself, in Lima, Peru April 17, 2019.

A mahout holds the chain of the temple's elephant during a ceremony as part of the Sinhala, Hindu and Tamil new year celebrations in Colombo, Sri Lanka April 17, 2019.

U.S. Sailors stand at parade rest during a Change of Command ceremony aboard the amphibious assault ship USS Wasp in Subic Bay, Philippines, April 13, 2019. Picture taken on April 13, 2019. Courtesy Benjamin F. Davella III/U.S. Navy

Activists of a local LGBT community put tape over their mouths as they protest against discrimination in Saint Petersburg, Russia April 17, 2019.

A mock space capsule of the C-Space Project Mars simulation base is seen at dusk in the Gobi Desert outside Jinchang, Gansu Province, China, April 16, 2019. Picture taken April 16, 2019.