Nasir, a legal adviser to the Afghan Air Force during the war, helped approve airstrikes against Taliban fighters. He is still in Afghanistan, where he has lived in hiding since the Taliban takeover in 2021 while awaiting approval to resettle in the United States.

He had passed background checks and needed only a medical exam to finish the process, he said. But this past week, he and tens of thousands of other Afghans found their paths to the United States blocked by an executive action signed by President Trump.

The order suspended a resettlement program that brings thousands of legal refugees to the country each year. Among the many now in limbo are Afghans who assisted the American war effort and are seeking a new start and a sense of security in the United States.

Nasir, a former lieutenant colonel who asked that his full name not be used, wrote in a text message that Mr. Trump had “not only disregarded the interests of Afghans in this decision, but also failed to consider the interests of the United States.”

“How can the world and America’s allies rely on the U.S. government?” he added.

The U.S. Refugee Admissions Program, in place since 1980, allows legal immigration for vetted people who have fled their home countries because of persecution, war or other threats. In suspending the program, Mr. Trump said that continuing it would burden communities that were not equipped to handle refugees.

Mr. Trump’s order, titled, “Realigning the United States Refugee Admissions Program,” takes effect on Monday. It says that the secretary of state and the homeland security secretary may admit refugees on a case-by-case basis, but only if they determine that it is “in the national interest and does not pose a threat to the security or welfare of the United States.”