Beijing ? Arms negotiators failed to agree on a deadline for North Korea to disable its nuclear facilities, the United States said Thursday, casting doubt on when Pyongyang will proceed with its promised disarmament after shuttering its sole operating reactor.

Assistant Secretary of State Christopher Hill entered the six-nation talks this week saying he hoped to get a commitment from the North to declare its nuclear programs and disable them by year’s end – rendering the communist nation unable to easily make more bombs.

But on the eve of the talks’ end today, he said the sides had agreed to have working groups of experts pore over technical details for those next steps before the top envoys from all sides endorse a timeframe.

The working groups likely will meet by the end of August, he said.

The reactor shutdown Saturday was the first step North Korea has taken to scale back its nuclear ambitions since the crisis began in late 2002, when the North reactivated its reactor.