Seoul - Christopher Hill, the chief US negotiator in the North Korean nuclear talks, arrived in North Korea Wednesday trying to save an agreement on the disablement of North Korea's nuclear weapons programme.

The US embassy in Seoul said Hill crossed the border between South and North Korea Wednesday mid-morning. He is attempting to overcome the current stalemate in bilateral talks.

After arriving in South Korea on Tuesday, Hill was quoted as saying by the Yonhap news agency that he was travelling to Pyongyang to make the verification of the North's nuclear declaration possible.

"We need to make sure that we are going to be able to verify their declaration, so let's see if we can come up with the measures or they allow us to verify the declaration," Hill said.

Talks were in a very difficult phase, he added.

Hill's trip is designed to save a three-stage agreement that is to see the dismantlement of North Korea's nuclear programmes.

Work on the second stage of the agreement, which includes submission by North Korea of a declaration of its nuclear programme and the disablement of its main nuclear facility, has been reversed because North Korea charges the United States with failing to live up to its promise to take the Stalinist state off the US list of state sponsors of terrorism.

Last week, North Korea announced it planned to restart work at its reprocessing facility at Yongbyon this week by testing it using nuclear material.

The United States said it would take the promised step to remove the country from its terrorism blacklist as soon as Pyongyang agreed to verification procedures of its nuclear disarmament, but no compromise has been reached on the issue.