President Trump held an extraordinary meeting on Wednesday with the president of Syria, Ahmed al-Shara, a day after announcing that the United States would lift sanctions on his country — a move that would ease the economic stranglehold on a nation that is seen as central to the stability of the Middle East.

It was the first time in 25 years that the two countries’ leaders had met, and another milestone in Syria’s bid to reintegrate itself into the international community after decades of isolation. The two men spoke for about half an hour just before a summit of Gulf leaders in Saudi Arabia, a White House official said.

Mr. Trump told Mr. al-Shara that “he has a tremendous opportunity to do something historic in his country,” according to a summary of the meeting from the White House press secretary, Karoline Leavitt. The president also urged Mr. al-Shara to take steps to normalize Syria’s relations with Israel, which have long been hostile, and to tell “all foreign terrorists to leave” the country, the summary said.

Mr. Trump met Mr. al-Shara at the invitation of Crown Prince Mohammed bin Salman, the de facto ruler of Saudi Arabia, who took part in the meeting.

President Recep Tayyip Erdogan of Turkey, which backed the insurgency that brought Mr. al-Shara to power, joined by phone. Prince Mohammed and Mr. Erdogan had both urged Mr. Trump to lift the sanctions on Syria, and they praised the move in the meeting on Wednesday, with the crown prince describing it as “courageous,” according to the White House summary.