WASHINGTON — President Trump’s pledge on Tuesday to cancel military exercises on the Korean Peninsula surprised not only allies in South Korea but also the Pentagon.

Hours after Mr. Trump’s announcement in Singapore, American troops in Seoul said they are still moving ahead with a military exercise this fall — Ulchi Freedom Guardian — until they receive guidance otherwise from the chain of command.

Lt. Col. Jennifer Lovett, a United States military spokeswoman in South Korea, said in an email that the American command there “has received no updated guidance on execution or cessation of training exercises — to include this fall’s schedule Ulchi Freedom Guardian.”

“We will continue with our current military posture until we receive updated guidance from the Department of Defense,” she added.