The United States said Monday that northeast Asia is threatened by North Korea's "bellicose rhetoric" rather by than the annual US-South Korean military maneuvers.

The exercises "are not a threat to the North," acting State Department spokesman Robert Wood said when asked if Washington might be misreading Pyongyang.

"What is a threat to the region is this bellicose rhetoric coming out of the North," Wood said.

US officials echo analysts who suspect Pyongyang has toughened its stance as it competes with other world hot spots for President Barack Obama's attention, but one expert says North Korea fears US-backed South Korea wants to absorb it.

The North went on combat alert Monday as US and South Korean troops began the 12-day exercise -- which it calls a rehearsal for invasion -- and warned that any attempt to block its upcoming satellite launch would spark a war.

Speaking at the daily press briefing, Wood said: "What we're trying to do, as I've said many times, is to get the North back to the table within the six-party framework, denuclearize the Korean Peninsula."

"We want to have a different type of relationship with the North, but the North knows what it needs to do and we want to get them back, as I said, in that framework of the six-party talks and go forward on denuclearization," he said.

The United States has been involved in negotiations with the two Koreas, Japan, China and Russia aimed at scrapping North Korea's nuclear program in exchange for energy aid under a landmark six-party agreement signed in 2007.

The negotiations have deadlocked over a dispute with North Korea over how to verify disarmament.

Secretary of State Hillary Clinton appears to believe that North Korea has engaged in a war of words with South Korea as part of a ploy to ensure the new Obama administration does not overlook its interests in the multilateral talks.

"North Korea is not going to get a different relationship with the United States while insulting and refusing dialogue with the Republic of Korea," Clinton warned during her tour of Asia last month.

And the State Department's acting deputy spokesman Gordon Duguid sounded a similar note on Friday after the North said it could not guarantee the safety of South Korean flights during the military exercises.

"North Korea's belligerent rhetoric is unwarranted and counterproductive to the goal of more constructive engagement," Duguid said.

However, analyst Selig Harrison suspects North Korea's harder line flows from different concerns.

He said last month that Pyongyang is taking a harder line in the nuclear talks as hawks now dominate defense policy after leader Kim Jong-Il was widely believed to have suffered a stroke last August.

Harrison, speaking at the Woodrow Wilson International Center for Scholars following a trip to Pyongyang, added that the harder line reflected fears that South Korea, under new President Lee Myung-Bak, wanted to absorb the North.

He said it was "a disastrous, historic mistake" for Lee to say he will review the North-South summit declarations of June 2000 and October 2007 because it served to "revive North Korean fears that South Korea, the United States and Japan want regime change and absorption.