But the broader question is what course President Trump might chart on Afghanistan. Senator John McCain, the Arizona Republican who chairs the Armed Services Committee, said that for too long the United States strategy had been “not to lose,” and urged that a plan be devised to break the stalemate.

General Nicholson said the administration was working on one. Michael T. Flynn, Mr. Trump’s national security adviser, served as an intelligence officer in Afghanistan. Mr. Mattis, Mr. Trump’s defense secretary, oversaw the military effort there when he served as the head of Central Command.

Mr. Trump has said little about Afghanistan, although on Thursday he held his second call since his election with Ashraf Ghani, the nation’s president.

“The two leaders spoke about the counterterrorism efforts, threat levels in Afghanistan, the capabilities of Afghan forces, as well as the risks of terrorism in the region and the countries that support terrorism,” said Nader Nadery, Mr. Ghani’s adviser on strategic affairs.

Mr. Nadery said troop levels were not a focus of the call. But Afghan officials say Mr. Ghani and Mr. Trump spoke about the possibility of increasing troop levels if a military assessment showed the need for it during their first conversation, in early December.

The war in Afghanistan is a topic the president has rarely discussed. “Hardly a word was mentioned by Trump about Afghanistan during the campaign, yet it remains one of the U.S.’s largest security expenditures,” said Daniel Feldman, who served as the senior envoy for Afghanistan and Pakistan during the Obama administration.

Mr. Feldman said that a broad assessment was needed of the terrorist threat, the role of international partners and how to pursue reconciliation between the Afghan government and the Taliban. But he said there was no indication that the new administration had begun such a review.