The U.N. special envoy for Yemen says negotiators from the country's warring sides have reached a deal to allow the resumption of humanitarian aid deliveries into the besieged city of Taiz.

Ismail Ould Cheikh Ahmed hailed "a major step forward" and a first important achievement in the U.N.-brokered peace talks in the Swiss village of Macolin, now in their third day.

A U.N. statement on Thursday also said a large convoy carrying humanitarian aid had reached Taiz, and deliveries are expected to reach other cities, including Hajja and Saada, in coming days.

It said talks will continue over the next few days with a focus on achieving a "sustainable national cease-fire," force withdrawals and the return of heavy weapons and control of public institutions to the state.