ANKARA, Turkey — After lengthy meetings with the Turkish president, Recep Tayyip Erdogan, Senator Lindsey Graham called on Saturday for a slower, smarter withdrawal of American troops from Syria to avoid setting off a broader war and a nightmare for Turkey.

Mr. Graham, Republican of South Carolina, has a long familiarity with Turkey and its place in the NATO alliance, and he said he was on a mission to ensure that the American withdrawal announced by President Trump in December did not cause greater damage that would be against United States interests in the long run.

“I can understand the desire to withdraw, but withdrawal without a plan is chaos,” he told a news briefing in Ankara, the Turkish capital. “It would be Iraq on steroids,” he warned, in a reference to how the Islamic State gained power after the withdrawal of American forces from the country in 2011.

Mr. Graham’s trip to Turkey came after an aborted visit by the White House national security adviser, John R. Bolton, who left the country without meeting with Mr. Erdogan. Infuriated by comments Mr. Bolton had made in Israel that Turkey would be forced to ensure that Kurdish forces were protected, Mr. Erdogan canceled a proposed meeting.