US Defence Secretary Lloyd Austin has made an unannounced visit to Afghanistan, weeks before a planned withdrawal of all remaining US troops.
After meeting President Ashraf Ghani in Kabul, he called for a responsible end to the war but would not say whether the deadline would be met.
Mr Austin said the focus should be on reducing high levels of violence to allow a negotiated end to the conflict.
The pullout was agreed with the Taliban by the Trump administration last year.
But there are questions over whether the insurgents have kept their pledge to negotiate with the Afghan government.
New US President Joe Biden has said the 1 May deadline would be tough to meet, prompting warnings of “consequences” from the Taliban.