Mr Kim will stop on Wednesday in China before heading on Thursday to North Korea for a visit expected to last up to three days. -- PHOTO: AFP

The North pledged to give the declaration by the end of last year and insists it has already done so, but Washington says it has not received a comprehensive list - a dispute that has mired the arms talks that began in 2003 in their latest deadlock.

US diplomat Sung Kim said on Tuesday he would press the North to deliver the atomic list 'as quick as possible'.

'The requirement is for a complete and correct declaration,' he said after arriving at Incheon International Airport outside the South Korean capital, Seoul, for meetings with South Korean officials.

Mr Kim will stop on Wednesday in China before heading on Thursday to North Korea for a visit expected to last up to three days.

'We'll try to make progress on the six-party talks,' he said, referring to the arms negotiations that include China, Japan, Russia, the US and the two Koreas.

US Secretary of State Condoleezza Rice said on Monday in Washington that she hopes the North is 'ready to have serious discussions' about its declaration, adding that its completion is 'necessary in order for further progress to be made on all of the obligations'.

The North has complied with a promise to disable its main plutonium-producing facility, which has gone beyond its Dec 31 deadline due to technical reasons.

The US, which once branded North Korea as part of an 'axis of evil', has shown unusual patience with the communist country after Washington reversed its hard-line stance following Pyongyang's Oct 2006 nuclear test.

A Chinese envoy was also expected to visit North Korea soon, Beijing's Foreign Ministry said.

'We hope the parties can remain patient and continue to work hard to implement the relevant agreements,' Foreign Ministry spokesman Jiang Yu told a regularly scheduled briefing. -- AP