In remarks made Wednesday aboard the presidential aircraft, Air Force One, Donald Trump said his administration’s pause on all asylum claims has no time limit, reiterating his tough stances on immigration and leaving open the possibility of stripping citizenship from some U.S. citizens.

The U.S. president said that his administration’s decision to freeze all consideration of asylum claims “has no time limit, but it could go on for a long time,” arguing that the United States “has enough problems already” and does not need additional immigration flows. “We don’t want these people. We have enough problems already,” Trump told reporters on Air Force One.

When asked to clarify whom he meant by “those people,” he replied that he was referring to “people from countries that are not friendly to the U.S. and countries that are out of control.” Trump added that many of those countries “are third-world, crime-plagued and not doing well,” noting: “Frankly, we don’t need their people coming into our country and telling us what to do.”

The U.S. president also reiterated his threat that he may revoke the citizenship of certain U.S. citizens. “If I have the power to do so — I’m not sure I have it, but if I do — I would revoke citizenship,” he said.