The United States takes seriously North Korea's war threats but has not seen any sort of large-scale mobilization of troops or positioning of forces by Pyongyang, the White House said on Monday.

"We haven't seen actions to back up the rhetoric," White House spokesman Jay Carney told reporters.North Korea said last week it is in a "state of war" with South Korea and issued other threats that heightened tension on the Korean Peninsula."I would note that despite the harsh rhetoric we are hearing from Pyongyang, we are not seeing changes to the North Korean military posture, such as large-scale mobilizations and positioning of forces," Carney said.

The United States flew two nuclear-capable stealth bombers over the Korean peninsula as part of a military exercise last week in a show of force to reassure U.S. allies in the region.The Pentagon has also been beefing up U.S. missile defense capabilities on the West Coast. The United States has stressed that it has the capability and willingness to protect itself and its allies in the region.

Carney said stealth bomber flights were important to reassure U.S. allies, "demonstrate our resolve to the North and reduce pressure on Seoul to take unilateral action."And we believe this has reduced the chance of miscalculation and provocation," he said. "I would also note this pattern of bellicose rhetoric is not new. It is familiar. And we take it very seriously, we take prudent measures in response to it, but it is consistent with past behavior.