The US special representative for Afghanistan has met with one of the founding members of the Taliban for the first time, as the latest round of peace talks resumed in Qatar Monday.

Zalmay Khalilzad tweeted that he had met with the organization’s second-in-command: “Just finished a working lunch with Mullah Baradar and his team. First time we’ve met. Now moving on to talks.”

The new round of negotiations follows an earlier meeting in January when representatives agreed in principle to a framework that could eventually bring Afghanistan’s long-running war to an end.

Earlier, Khalilzad announced his arrival in Qatar’s capital, Doha, saying he was meeting “with a more authoritative Taliban delegation. This could be a significant moment.”

Taliban spokesman Zabiullah Mujahid said in a statement “ending of occupation and issue of terrorism” were on the agenda.

The conflict, known as America’s longest war, has spanned over 17 years, cost more than 2,400 American lives, billions of US dollars and has stretched into its third US administration.

More than 45,000 Afghan security personnel have “paid the ultimate sacrifice” since 2014, Afghan President Ashraf Ghani said in January at the World Economic Forum’s Annual Meeting in Davos, Switzerland.