'By working together and by coordinating closely among the six parties, we hope to convince chairman Kim Jong-Il to make the right choice,' US ambassador to Seoul Alexander Vershbow said.

Mr Sung Kim, the US State Department's top Korea expert, was in Pyongyang on Thursday to 'help jumpstart the process' at the same time a Chinese envoy was in the North Korean capital, Mr Vershbow told a forum of the Korea Economic Institute in Washington.

Mr Sung Kim 'has had some preliminary meetings' with North Korean foreign ministry officials, department spokesman Sean McCormack told reporters in Washington.

'He expects to have some more tomorrow,' he added without giving details.

The Chinese state media reported on Thursday that North Korean leader Kim told China's visiting senior Communist party official Wang Jiarui that he still backed the six-nation deal, under which the impoverished nation stands to gain more badly needed fuel aid and security guarantees.

The North was supposed to declare and disable its main atomic plants by the end of 2007 under the six-nation deal negotiated by the two Koreas, China, the United States, Russia and Japan.

North Korea has said it submitted a list in November, but the United States says it is still waiting for a complete declaration, including a full account of a suspected covert uranium enrichment program.

North Korea, which staged a nuclear test in October 2006, has accused Washington of bad faith and warned it could slow down cooperation.

Mr Vershbow said the United States believed that 'with political will on North Korea's part, we can achieve a comprehensive solution' to the nuclear crisis this year, but stressed 'we will not settle for less than full denuclearisation.

'We obviously have had difficulty persuading the North Koreans of the need to acknowledge some of their past procurement activities regarding uranium enrichment and issues relating to cooperation with third countries,' he said.

'We are continuing to persevere.' The United States says it has evidence that North Korea bought uranium enrichment technology and received assistance from Pakistan but does not know whether its uranium program is up and running now.

Washington suspects that Pyongyang received uranium enrichment centrifuges from the nuclear black market network once operated by top Pakistani nuclear scientist Abdul Qadeer Khan.

North Korean officials denied any operation
North Korean officials have denied operating any uranium program alongside its known plutonium weapons efforts.

'Why don't you invite AQ Khan to join the negotiations?,' Mr Kim Myong Gil, North Korean envoy to the United Nations, told a US expert on Asia Selig Harrison recently.

'Where is the invoice? Give us the evidence,' Mr Harrison quoted the envoy as telling him, according to the expert's commentary in the Washington Post on Thursday.

Mr Khan provided 'nearly two dozen' prototype centrifuges suitable for uranium enrichment experiments to North Korea, Pakistan President Pervez Musharraf wrote in his memoir, 'In the Line of Fire,' released more than a year ago.

Mr Musharraf has not allowed international investigators to question Mr Khan, saying that Mr Khan's illegal nuclear network had no state support. -- AFP