The US envoy to talks on North Korea's nuclear program said Tuesday a tentative agreement had been reached on initial steps for Pyongyang's disarmament, setting the stage for the first concrete progress after more than three years of negotiations. US Assistant Secretary of State Christopher Hill declined to give details of the draft, but said it outlined specific commitments for Pyongyang and would set up working groups to implement those goals to begin meeting in about a month. "I'm encouraged by this that we were able to take a step forward on the denuclearization issue," a weary-looking Hill told reporters after a fifth day of negotiations at talks in Beijing that lasted more than 16 hours. The agreement could mark the first step toward disarmament since the talks began in 2003, marked by repeated delays and deadlock. The process reached its lowest point in October when North Korea conducted its first nuclear test explosion.