SEOUL, SOUTH KOREA - After months of rising tensions and bellicose rhetoric, North Korea has signalled it wants better relations with arch enemy the United States by inviting former President Bill Clinton, analysts say.

Clinton arrived Tuesday on a surprise visit to the communist state. South Korean media said his mission was to negotiate the release of two US female journalists jailed for 12 years for an illegal border crossing.

Seoul analysts said that - for Pyongyang at least - the trip will also have a political dimension, with Clinton highly likely to meet leader Kim Jong-Il as well as to fly home with the women.

They said the visit could warm icy relations between the North and the United States and its allies, following Pyongyang's nuclear and missile tests this spring and subsequent tougher United Nations sanctions.

But some cautioned against expecting any dramatic breakthrough in the decades-old nuclear standoff.

Kim Yong-Hyun, a North Korea studies professor at Dongguk University, said the former US leader was expected to discuss a series of political issues including the nuclear programme.

"There will be no major breakthrough with his trip alone but I believe it will provide a fresh momentum for nuclear disarmament talks," Kim said.

"It is also possible for North Korea and US to start bilateral talks in parallel with six-party negotiations."

Cheong Seong-Chang of the Sejong Institute think-tank said the North Korean side was seeking a breakthrough in relations by allowing the visit.

"It will also be used for domestic propaganda as it comes amid growing concerns about Kim's health," Cheong said.

Kim, 67, is widely believed to have had a stroke last August.

US and South Korean officials say the North's recent hardline behaviour - including multiple missile launches and a nuclear test - is aimed at shoring up Kim's authority while he puts in place a succession plan involving his youngest son.

"With Clinton's trip, Pyongyang will seek to improve relations with Washington or to end the current tense standoff over its nuclear test and UN sanctions," Cheong told AFP.

Clinton's visit "will pave the way for bilateral talks on a package of issues including the North's nuclear programme," he said.

"Yet it may not come back to six-party negotiations for a while. North Korea will resume six-party negotiations only when there is considerable progress in bilateral talks."

The North quit the six-party talks after the UN censured its long-range rocket launch in April. Last week it again dismissed the forum but indicated willingness for direct talks with Washington.

The Obama administration has not rejected direct dialogue but is eager not to sideline the six-party forum, which groups the two Koreas, China, Russia, Japan and the United States.

It says the fate of the journalists should not be linked to the nuclear standoff.

Yang Moo-Jin, a professor at Seoul's University of North Korean Studies, noted that senior officials received Clinton at the airport.

"It was sending a signal that it was treating the former US leader with great hospitality and also that it was willing to have a political dialogue, including nuclear disarmament."

Paik Haksoon, also from the Sejong Institute, said Clinton is certain to meet Kim. "Clinton's visit will usher in a new era of US-North Korean relations," Paik said.

But the North, while insisting its atomic weapons are for defensive purposes only, still wants to be recognised as a nuclear power. The US and its regional allies say this is out of the question.

Denny Roy, senior fellow at the Honolulu-based East-West Center, told Yonhap News Agency the visit will not necessarily lead to any breakthrough in the overall relationship.

"If North Korea is not prepared to negotiate denuclearisation and the US is not prepared to accept North Korea as a nuclear weapon state, the relationship will remain at an impasse," he said.