When it comes to Afghanistan, Mr. Trump entered office as the skeptic in chief, and any ramped-up engagement there poses political risks for the president, who rallied voters weary of war with his sharp criticisms of American involvement in the country.

“We should have a speedy withdrawal. Why should we keep wasting our money — rebuild the U.S.!” Mr. Trump tweeted about Afghanistan in January 2013, as he considered running for office in 2016.