A spokesman for the Joint Chiefs of Staff, Col. Patrick Ryder, said he had no information about troop options being prepared for the president.

For Mr. Trump, withdrawing troops would have multiple benefits, said Victor D. Cha, a Korea scholar at Georgetown University who was for a time under consideration to be ambassador to Seoul. It would appeal to his political base, save the United States money and give him a valuable chit in his negotiation with Mr. Kim.