SEOUL - SOUTH Korea warned North Korea on Thursday to scrap any plans to launch its longest-range missile, saying this would violate United Nations resolutions passed after the last test in 2006.

Officials in Seoul and Washington say there are signs the communist state is preparing to test the Taepodong-2, which has a range of 6,700 kilometres and could theoretically target Alaska.

The reports, based on satellite photos, come amid stalled six-nation nuclear disarmament talks and rising inter-Korean tensions. The North has scrapped a non-aggression pact with the South and warned of possible conflict.

Pyongyang, in what some analysts see as a message to the new US administration, has also staked out a tough negotiating position in the disarmament talks involving the US and four regional powers.

Seoul's foreign ministry refused comment on reports of launch preparations but said any such move would breach UN Security Council resolutions.

'The UNSC in 2006 adopted Resolutions 1695 and 1718, expressing serious concerns over the North's missile programme and delivering a firm message,' spokesman Moon Tae-Young told a briefing. 'If the North lobs a missile, it would constitute a clear breach of the UN resolution.'

The US State Department has said any test would be 'provocative.' The North carried out long-range missile tests in 1998 and 2006, sparking international condemnation. Experts disagree on whether it is technically capable of fitting the missiles with a nuclear warhead.

The Taepodong-2 launched in 2006 failed after 40 seconds, according to US officials. A Seoul government source told Yonhap news agency the missile spotted recently is believed to be a modified version.

The last round of six-party talks ended in deadlock in December because of disagreements over ways to verify the North's atomic disclosures.

Relations with South Korea soured last spring, after conservative President Lee Myung-Bak took office and rolled back the 'sunshine' engagement policy of his liberal predecessors.

Mr Lee linked major economic aid to denuclearisation and said he would review summit pacts signed by the North and his predecessors.

A US expert who visited Pyongyang last month described Lee's stance on the summit deals as a 'disastrous, historic mistake.'

Selig Harrison told a Washington think-tank the posture served to 'revive North Korean fears that South Korea, the United States and Japan want regime change and absorption.

'They're especially sensitive about this with Kim Jong-Il ill,' he said on Wednesday.

Leader Mr Kim, who turns 67 this month, is widely reported to have suffered a stroke last August. Mr Harrison said hawks have come to dominate defence policy since then.

'North Korea has suddenly adopted a much harder line (in six-party negotiations) than before and the question is why,' he said.

Though some analysts believed it was a 'bargaining posture' aimed at the new US administration, Mr Harrison stressed the fallout from the leader's illness and political changes in South Korea as contributing factors.

The scholar, confirming earlier reports, said he believes Mr Kim has a greatly reduced work schedule.

'He has turned over day-to-day management of domestic affairs to his brother-in-law Jang Song-Taek and foreign affairs and defence policy is now largely in the hands of hawks in the National Defence Commission,' Mr Harrison said. -- AFP