“While we don’t believe the existence of settlements is an impediment to peace,” his press secretary, Sean Spicer, said in a statement, “the construction of new settlements or the expansion of existing settlements beyond their current borders may not be helpful in achieving that goal.”

The White House noted that the president “has not taken an official position on settlement activity.” It said he would discuss the issue with Prime Minister Benjamin Netanyahu of Israel when they meet Feb. 15, in effect telling Mr. Netanyahu to wait until then. Emboldened by Mr. Trump’s support, Israel has announced more than 5,000 new homes in the West Bank since his inauguration.

Mr. Trump shifted his policy after he met briefly with King Abdullah II of Jordan on the sidelines of the National Prayer Breakfast — an encounter that put the king, one of the most respected leaders of the Arab world, ahead of Mr. Netanyahu in seeing the new president. Jordan, with its large Palestinian population, has been steadfastly critical of settlements.

The administration’s abrupt turnaround also coincided with Secretary of State Rex W. Tillerson’s first day at the State Department and the arrival of Defense Secretary Jim Mattis in South Korea on his first official trip. Both men are viewed as potentially capable of exerting a moderating influence on the president and his cadre of White House advisers, though it was unclear how much they had to do with the shifts.

With Iran, Mr. Trump has indisputably taken a harder line than his predecessor. While the Obama administration often looked for ways to avoid confrontation with Iran in its last year, Mr. Trump seems equally eager to challenge what he has said is an Iranian expansion across the region, especially in Iraq and Yemen.

In an early morning Twitter post on Thursday, Mr. Trump was bombastic on Iran. “Iran has been formally PUT ON NOTICE for firing a ballistic missile,” he wrote. “Should have been thankful for the terrible deal the U.S. made with them!” In a second post, he said wrongly, “Iran was on its last legs and ready to collapse until the U.S. came along and gave it a life-line in the form of the Iran Deal: $150 billion.”