Military and defense

Police seal off the Champs Elysees avenue in Paris, France, after a fatal shooting in which a police officer was killed along with an attacker, Thursday, April 20, 2017. French media are reporting that two police officers were shot Thursday on the famed shopping boulevard. Many police vehicles can be seen on the avenue that passes many of the city's most iconic landmarks. (AP Photo/Kamil Zihnioglu)

President Donald Trump speaks during a news conference with Italian Prime Minister Paolo Gentiloni in the East Room of the White House in Washington, Thursday, April 20, 2017. (AP Photo/Susan Walsh)

President Donald Trump signs an executive memorandum on investigation of steel imports, Thursday, April 20, 2017, in the Oval Office of the White House in Washington. (AP Photo/Susan Walsh)

FILE - In this Nov. 21, 2016 file photo, former Massachusetts Sen. Scott Brown talks with media at Trump Tower in New York. President Donald Trump has announced plans to nominate Brown to be the U.S. ambassador to New Zealand. (AP Photo/Carolyn Kaster, File)

FILE - In this Jan. 21, 2017 file photo, a crowd fills Independence Avenue during the Women's March on Washington, in Washington. The major protests in Washington that have greeted President Donald Trump’s first year in office are set to return in force, continuing an already expensive year for city officials who work to keep people safe during mass gatherings. (AP Photo/Alex Brandon, File)

FILE - In this Tuesday, April 18, 2017, file photo, President Donald Trump gives a thumbs-up as he walks to board Marine One on the South Lawn of the White House in Washington, for the short trip to Andrews Air Force Base, Md., en route to Kenosha, Wis. Trump, the "America First" president who vowed to extricate the U.S. from onerous overseas commitments, appears to be warming up to the view that when it comes to global agreements, a deal's a deal. (AP Photo/Carolyn Kaster, File)

In this undated photo provided by the National Immigration Law Center shows Juan Manuel Montes, 23. The U.S. Department of Homeland Security reverses itself on the status of Montes, who may be the first person who qualifies for a program to shield young immigrants to be deported by President Donald Trump. Authorities now acknowledge that Montes, qualified for the Deferred Action for Childhood Arrivals program but still defend the decision to return him to Mexico. (Juan Gastelum/National Immigration Law Center via AP)

European Council President Donald Tusk tells reporters the case in which he was questioned for over eight hours as a witness in Warsaw, Poland, is of highly political character, Wednesday, April 19, 2017. The investigation deals with alleged secret illegal contacts between Polish and Russian intelligence officials at a time when Tusk was Poland's prime minister from 2007-2014. (AP Photo/Czarek Sokolowski)