The United States and the Taliban have expressed optimism about the latest round of talks aimed at ending the 17-year war in Afghanistan.

U.S. envoy Zalmay Khalilzad says the talks, which carried into their second day on Tuesday, represent a "significant moment." The Taliban have also indicated progress, and the presence of Mullah Abdul Ghani Baradar, a co-founder of the movement and veteran battlefield commander, has further raised expectations.

The closed-door discussions in Qatar, where the Taliban maintain a political office, are believed to be focused on a U.S. troop withdrawal from Afghanistan and on launching negotiations between the Taliban and the U.S.-backed government in Kabul.