SEOUL, South Korea - North Korea's positioning of a rocket on its east coast launchpad ratcheted up tension with Washington on Thursday, which warned pushing ahead with the April launch would violate a UN ban and have serious consequences.

Pyongyang says the rocket is designed to carry its Kwangmyongsong-2 satellite into orbit, an accomplishment timed for the eve of the inaugural session of North Korea's new legislature and for late founder Kim Il Sung's April 15 birthday.

But regional powers suspect the North will use the launch to test the delivery technology for a long-range missile, one capable of striking Alaska, or may even test-fire the intercontinental Taepodong-2 missile itself. Keeping speculation about the payload alive, North Korea reportedly has covered the top of the rocket.

U.S. National Intelligence Director Dennis Blair said Pyongyang is trying to cloak the continued development of its outlaw long-range missile program by using a Taeopodong-2 missile to place a small satellite into orbit. He would not say whether the rocket is being fuelled.

"I think North Korea is attempting to demonstrate an ICBM (intercontinental ballistic missile) capability through a space launch," he said in Washington on Thursday.

"That's what they are up to -- trying to use the rationale of a legitimate space launch for a missile which is, in its foundation, a military missile: the Taepodong."

He said North Korea risks "international opprobrium and hopefully worse if they successfully launch or launch it at all."

White House press secretary Robert Gibbs on Thursday reiterated comments made a day earlier by U.S. Secretary of State Hillary Clinton that any rocket launch would be "provocative" and violate UN Security Council resolutions.

Clinton warned the launch could jeopardize stalled talks on supplying North Korea with aid and other concessions in exchange for dismantling its nuclear program.

The UN Security Council banned North Korea from any ballistic activity in 2006.

"We intend to raise this violation of the Security Council resolution, if it goes forward, in the U.N.," Clinton said Wednesday in Mexico City.

"This provocative action in violation of the UN mandate will not go unnoticed and there will be consequences."

North Korea responded by threatening "strong steps" if the Security Council so much as criticizes the launch and suggested it will reverse nuclear disablement carried out so far if sanctions are levied. Any challenge to its satellite launch would mean an immediate nullification of disarmament agreements, the Foreign Ministry said in a statement carried late Thursday by the Korean Central News Agency.

Analysts said the diplomatic tussle puts North Korea right where it wants to be: at the centre of Washington's attention.

"This action is something that cannot be ignored...This is a way to get attention from the U.S. and the Obama administration," said Daniel Pinkston, a Seoul-based analyst for the International Crisis Group think-tank.

"The North Korean leadership probably believes this will help achieve their objective of engaging the U.S."

Analysts say Pyongyang is angling to establish direct relations with President Barack Obama's White House in hopes of circumventing the international disarmament talks that require the North dismantle its nuclear program in exchange for aid.

Complicating the diplomacy is the detention of two U.S. journalists, Euna Lee and Laura Ling of former U.S. nice-president Al Gore's Current TV media outlet, for allegedly crossing into North Korea illegally from China last week.

The Americans are an "unexpected gift" the North may use as bargaining chips in their push for direct talks, said North Korea expert Koh Yu-hwan of Dongguk University.

"The timing couldn't be better for North Korea," Pinkston said.

"It strengthens the North's bargaining position with the U.S. in dealing with the nuclear issue."

North Korea last month announced its plans to shoot a satellite into space, notifying aviation and maritime authorities the launch would occur April 4-8.

U.S. spy satellites spotted the rocket earlier this week, South Korean reports said. Counterterrorism and intelligence officials in Washington confirmed a rocket was in position.

After mounting it, scientists need several days to test and fuel the rocket, analysts said. North Korea is now "technically" capable of launching it in three to four days, South Korea's Chosun Ilbo newspaper said, citing an unnamed diplomatic official.

South Korean and U.S. intelligence authorities have not yet determined whether the rocket is intended to carry a satellite or a missile because the top is concealed with a cover, the Yonhap news agency said, citing an unnamed South Korean government official.

One analyst called it a possible smokescreen designed to invite speculation.

"I think North Korea is trying to raise as much attention as it can by covering (the top) so that it cannot be verified and it will create confusion," said Yang Moo-jin, a professor at the University of North Korean Studies.

Missiles and satellites share the same delivery technology so either way, next month's launch "would contribute to the development of its ballistic capacities," French Foreign Ministry spokesman Frederic Desagneaux said in Paris.

North Korea is not believed to have mastered the miniaturization technology required to mount a nuclear weapon onto a ballistic missile but successfully test-firing the rocket would be a step toward developing a means to deliver a nuclear weapon, Koh said.

Seoul warned a launch would threaten regional stability and said it would take the matter to the Security Council.

Chinese Foreign Ministry spokesman Qin Gang urged restraint, saying he hoped all parties would "do things to contribute to peace and stability on the peninsula."

Japan wasn't taking any chances. Spooked by a rocket launch a decade ago and North Korea's attempt to launch a long-range missile in 2006, Tokyo is preparing to shoot down debris or fragments if the launch -- which is expected to pass over the north of the country -- fails.

Defence Minister Yasukazu Hamada on Friday ordered a deployment of land-to-air and sea-to-air interceptor missiles in northern Japan. Officials set up hot lines and conducted safety drills along the northern coast.

The U.S. navy has two Aegis-equipped ships now docked at South Korea's Busan port, military spokesman Kim Yong-kyu said. Japan also reportedly plans to deploy an Aegis radar-equipped destroyer carrying a missile interceptor and South Korea also will dispatch a destroyer to monitor the launch, Yonhap said.