KABUL, Afghanistan — U.S. officials say some progress has been made in U.S. Secretary of State JohnKerry’s talks with Afghan President Hamid Karzai on a security deal to allow American troops to remain in the country after the NATO-led military mission ends next year.

The officials said talks were extended Saturday on a bilateral security agreement that the United States wants by the end of October. They were speaking on condition of anonymity because they weren’t authorized to discuss the negotiations.

Kerry’s unannounced overnight visit to Kabul comes as talks foundered over issues of Afghan sovereignty despite a year of negotiations.

Talks resumed Saturday as they tried to resolve Karzai’s demand for guarantees against future foreign intervention, and U.S. demands that a residual force be able to conduct counterterrorism operations.