North Korea's envoy to nuclear talks warned Saturday that Pyongyang will slow work on dismantling its nuclear program if energy aid by Washington and others is delayed.

Four days of disarmament talks ended in a stalemate last week after North Korea refused to make written commitments on inspection of its nuclear program. That blocked progress on an aid-for-disarmament agreement reached last year.

"Let's watch whether economic and energy compensation projects stop or move forward," the North Korean envoy, Kim Kye Gwan, said as he prepared to return to Pyongyang. "We'll adjust the speed of our disablement work if it (energy aid) doesn't come in."

South Korea's foreign minister said Thursday the North might be trying to extract more aid by resisting verification of the dismantling of its nuclear program.

Pyongyang complained Wednesday about a delay in energy aid, saying it has slowed disabling the Yongbyon reactor in response. It refused to allow outside inspectors to take samples from its main nuclear complex in Yongbyon.

North Korea has agreed to give up nuclear weapons but has resisted Washington's attempts to put in place strict measures to ensure it is not hiding any active atomic programs.

U.S. officials said last month North Korea agreed to let atomic experts take samples and conduct forensic tests at all of its declared nuclear facilities and undeclared sites. That is believed to be a key means of nuclear verification.

The North agreed in February 2007 to disable Yongbyon and declare all its nuclear programs as a step toward their ultimate dismantlement. In exchange, the impoverished communist nation was promised energy aid worth 1 million tons of fuel oil and other concessions, including removal from the U.S. list of terrorist sponsors.