North Korea's new rocket launch plans are a dramatic gesture of defiance towards the international community, and a major challenge to the winner of South Korea's upcoming presidential elections, analysts say.

Pyongyang announced Saturday it was preparing to carry out its second long-range rocket launch of the year -- ostensibly aimed at placing a satellite in orbit -- following a much-hyped but failed attempt in April.

The announcement was made in the face of a UN Security Council warning just days before that going ahead with the launch would be "extremely inadvisable"

The United States and its key Asian military allies, South Korea and Japan, insist the launch is a disguised ballistic missile test that violates UN resolutions triggered by Pyongyang's two nuclear tests in 2006 and 2009.

Professor Yang Moo-Jin of the University of North Korean Studies in Seoul warned that North Korea and its leader Kim Jong-Un were embarking on a high-stakes game of brinkmanship with the international community.

The launch, and in particular a successful launch, would likely draw sanctions, either from individual countries or concerned nations acting as a bloc.

"The North then would react strongly, probably upping its nuclear activity and possibly carrying out a third nuclear test," Yang said. "And so we get into a vicious circle of escalating tensions."

Both of North Korea's previous nuclear tests were held one to three months after missile tests.

Condemnation of the North's plans to launch a rocket between December 10 and 22 was rapid, with both the United States and South Korea denouncing what they termed a "highly provocative" act.

"Devoting scarce resources to the development of nuclear weapons and long-range missiles will only further isolate and impoverish North Korea," US State Department spokeswoman Victoria Nuland said.

Tokyo said it was postponing talks between senior Japanese and North Korean diplomats scheduled to take place in Beijing this week.

The North's announcement comes at a time of transition for four of the countries involved in the stalled six-country talks on North Korea.

Japan will hold a general election on December 16, while South Korea will elect a new president on December 19

China, North Korea's main source of economic aid, has just completed its once-in-a-decade transition to a new leadership, and US President Barack Obama is preparing to start on his second term in office.

The launch window provided by Pyongyang also coincides with the one-year anniversary of leader Kim Jong-Un's assumption of power following the death of his father Kim Jong-Il on December 17.

The potential political impact is particularly strong for South Korea, where the two main presidential candidates have both signalled the need for greater engagement with Pyongyang.

Analysts say the ruling conservative party candidate Park Geun-Hye, daughter of the late former military strongman Park Chung-Hee, is most likely to benefit if a rocket launch pushes voter sentiment towards a harder line with the North.

"The launch will make more South Koreans feel disappointed and disillusioned about the North... which eventually helps Park," said Baek Seung-Joo of the Korea Institute of Defence Analyses.

Although Park has expressed a willingness to build bridges with Pyongyang, her party is seen as the more hawkish, especially compared to the opposition Democratic United Party of her liberal rival Moon Jae-In.

"Even if Park really wants reconciliation with the North, she will get little backing from her party and main constituents," said Paik Hak-Soon, a senior analyst with the Sejong Institute think tank.

"So she faces a really tough road ahead in cross-border ties for the next five years," Paik told AFP.

Moon is best known as a top aide to former president Roh Moo-Hyun, whose administration had continued the "sunshine policy" of engagement and aid to North Korea pioneered by his predecessor Kim Dae-Jung.