WASHINGTON (Reuters) - U.S. President Donald Trump said on Sunday that White House Council of Economic Advisers Chairman Kevin Hassett will “shortly” leave his post, but did not provide a reason for the latest high-level departure from the administration.

“Kevin Hassett, who has done such a great job for me and the Administration, will be leaving shortly. His very talented replacement will be named as soon as I get back to the U.S.,” Trump said in a Twitter post on Sunday night as he flew to Europe for a series of state visits.

Hassett’s impending departure comes at a time of drama between the United States and some of its main trade partners. A trade war is brewing between the United States and China, while Trump has vowed to impose punitive tariffs on all Mexican goods in an intensifying dispute over migration.

Hassett previously served as a scholar of fiscal policy at the conservative American Enterprise Institute think tank before Trump nominated him to the White House role in 2017. In the White House post, he worked with Trump’s senior adviser and son-in-law Jared Kushner on a proposed immigration plan that the Republican president unveiled in May and had backed a U.S. move to end waivers of sanctions for countries that buy Iranian oil.

Trump thanked Hassett for his work, and called him a “true friend” in the Twitter post on Sunday. He did not give any indication on who he would name to replace Hassett.

Hassett is poised to become the latest in a long line of senior White House officials and Cabinet secretaries to depart the administration since Trump took office in January 2017.

Others who have resigned or been ousted this year alone include Homeland Security Secretary Kirstjen Nielsen, White House communications director Bill Shine and Small Business Administration chief Linda McMahon.

The chairman of the Council of Economic Advisers serves as the chief economic adviser to the administration as a whole. The council’s work is research-focused and less concerned with coordinating policy across agencies than the National Economic Council, a separate advisory body currently led by Larry Kudlow.

Trump departed on Sunday night for a trip that takes him to Britain, where he is scheduled to meet with members of the royal family, before going to Ireland and then France to attend ceremonies marking the 75th anniversary of the World War Two allied D-Day invasion.