Michele Kelemen

Updated at 8:08 p.m. ET

President Trump has chosen John Bolton, a hawk on North Korea and Iran, to be his next national security adviser.

The appointment comes just as those two foreign policy challenges come to a head.

Bolton replaces H.R. McMaster, who Trump said Thursday via Twitter is leaving the administration. Bolton takes over from McMaster effective April 9, the president also said.

AILSA CHANG, HOST:

The Trump administration is withholding half of its planned aid to the United Nations agency that helps Palestinian refugees. The former U.S. Army officer who directs the U.N. Relief and Works Agency in the West Bank is in Washington, trying to figure out what it will take to have that money restored.

Before heading to the White House, Scott Anderson spoke to NPR on Wednesday about the case he is making.

The United States contributed $60 million to UNRWA this year but is withholding another $65 million for further consideration.

In the dimly lit basement of what was once a soccer stadium in the northern Syrian city of Raqqa, CENTCOM commander Gen. Joseph L. Votel and Mark Green, the U.S. Agency for International Development administrator, walked through the rubble on Monday and listened to a U.S. military escort tell stories about what went on there when the city was under ISIS control.

The great mystery behind what hurt two dozen U.S. diplomatic personnel in Cuba remains unsolved, according to a Senate hearing on Tuesday. But an FBI investigation is casting doubt on a once-popular theory: that embassy staff were the victims of "sonic attacks."

According to a report seen by the Associated Press, an FBI investigation has turned up no evidence that sound waves harmed American diplomats in Havana.

The Middle East is a region that is used to diplo-speak. When U.S. officials talk about the Israeli-Palestinian conflict, they usually parse their words carefully. President Trump, though, is changing that, and it is causing confusion.

Last month, U.S. Ambassador to the United Nations Nikki Haley explained to the world that although the administration decided to recognize Jerusalem as Israel's capital, its final status is still up for negotiation.

In summing up his year, Secretary of State Rex Tillerson told a State Department town hall meeting in mid-December he has no diplomatic wins on the board. "Diplomacy is not that simple," he said. But Tillerson believes his restructuring plan — which includes improving IT systems and streamlining the bureaucracy — has put the State Department in a better place.