ISLAMABAD (AP) — Officials say Washington's peace envoy is in the Afghan capital Kabul trying to negotiate a prisoner exchange that would free America Kevin King and Australian Timothy Weeks, two professors at the American University held by the Taliban since 2016.

Zalmay Khalilzad was in Kabul on Thursday trying to barter a prisoner exchange that could resuscitate peace efforts to end Afghanistan's 18-year war, America's longest, they said.

The officials, who are familiar with Khalilzad's efforts, spoke on condition of anonymity because they are not authorized to speak to the media.

Among others, the Taliban are demanding the release of Anas Haqqani, the younger brother of Sirajuddin, deputy head of the Taliban and leader of the Haqqani network, often considered the strongest of the Taliban fighting in Afghanistan.

Associated Press writer Deb Riechmann in Washington contributed to this report.