The officials also regretted that North Korea had now barred UN inspectors from its nuclear sites following its moves to restart a nuclear program it had shut down last year under the six-party disarmament negotiations.

"We would urge North Korea to avoid any steps that increase tension on the peninsula," State Department spokesman Sean McCormack told reporters when asked about rising tensions over the disputed Korean maritime borders.

Two days after it fired short-range missiles in the Yellow Sea, North Korea on Thursday accused South Korean ships of violating its territorial waters there and warned that escalating tensions could lead to a clash.

McCormack could not confirm whether North Korea had test-fired missiles, but added: "I would remind the North Korean government ... that missile-related activities are prohibited under UN Security Council Resolution 1718."

The North Korean state news agency KCNA quoted a navy command spokesman as warning that "a naval clash may break out" over what he called the "ceaseless infiltration of warships deep into" North Korean waters.

He accused the South's navy of sending more warships into the North's territorial waters since early September in an attempt to legitimize the disputed sea border known as the Northern Limit Line (NLL).

The two Koreas have remained technically at war since their 1950-1953 conflict ended in a fragile armistice, rather than a peace treaty.

North Korea has never recognized the sea border with the South that was drawn up by a US-led UN Command after the war.

The area was the scene of bloody naval skirmishes in 1999 and again in June 2002, when six South Korean sailors were among the dead.

McCormack said he could not comment on the motives of the isolated communist North Korean government when asked if Pyongyang was upping the ante over the nuclear negotiations.

Meanwhile, there was no sign that North Korea and its five negotiating partners -- the United States, China, South Korea, Japan and Russia -- were close to breaking the nuclear deadlock.

In Vienna, the International Atomic Energy Agency (IAEA), the UN nuclear watchdog, said Pyongyang had informed the agency that its inspectors at the Yongbyon nuclear reactor complex were now denied access.

Pyongyang announced in September that it planned to restart its nuclear reprocessing plant at Yongbyon, used to make weapons-grade material, and that IAEA inspectors would have no further access to it.

"It's a regrettable step but one that is reversible," McCormack said.

The spokesman said that other steps North Korea has taken -- such as removing seals on equipment and putting equipment back in place -- were reversible.

Under a six-nation deal reached in 2007 North Korea began disabling -- with a view toward total disarmament -- its nuclear weapons programs in exchange for energy and other aid.

Pyongyang accuses Washington of breaching the deal by failing to remove it from a terrorism blacklist. The United States says the North must first agree to outside verification of a nuclear declaration it submitted in June.

The North, which conducted a nuclear test explosion in 2006, counters that verification is not part of this stage of the agreement.

The White House said Thursday it hopes to remove North Korea from the blacklist but will only do so if Pyongyang agrees to a verification protocol as part of denuclearization efforts.

"If we can get a verification protocol that we are satsified with, then we would be able to fulfill our side of the bargain," spokeswoman Dana Perino told reporters.

Related Links
Learn about nuclear weapons doctrine and defense at SpaceWar.com
Learn about missile defense at SpaceWar.com
All about missiles at SpaceWar.com
Learn about the Superpowers of the 21st Century at SpaceWar.com

Memory Foam Mattress Review

SPACE MEDIA NETWORK PROMOTIONS Solar Energy Solutions Tempur-Pedic Mattress Comparison ... Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News