"[Despite] the harsh rhetoric we're hearing from Pyongyang, we are not seeing changes to the North Korean military posture, such as large-scale mobilizations and positioning of forces," White House press secretary Jay Carney said during Monday's media briefing.
The United States is committed to keeping peace and security in the region, Carney said, and has taken prudent actions to do so.
North Korea has reacted angrily to U.S.-South Korean military drills and the latest round of U.N. and U.S. sanctions after Pyongyang's Feb. 12 underground nuclear test.
U.S. F-22 stealth jet fighters were poised in South Korea for war games Monday as North Korea said its nuclear-weapons program was non-negotiable. The U.S. military command in South Korea said it flew the fighter aircraft, known as the Raptor, to Osan Air Base, 40 miles south of Seoul, from Japan's Kadena Air Base near Okinawa, to showcase its most potent weaponry to North Korea.
"The actions we've taken are prudent," Carney said, nothing that they were being offered "to reassure our allies, demonstrate our resolve to the North, and reduce pressure on Seoul to take unilateral action. And we believe this will reduce the chance of miscalculation and provocation."
Carney said North Korea's actions aren't anything new but "we take it very seriously. We take prudent measures in response to it. But it is consistent with past behavior."
U.S. Sen. Bob Corker, R-Tenn., the top Republican on the Senate Foreign Relations Committee, said on MSNBC Monday he didn't personally think the situation would escalate unless "an incident gets out of hand."
"It's my personal belief," said Corker, who just returned from South Korea, "that nothing is going to happen ... ."
He said North and South Koreans were still working together in an industrial area.
"I do not think anything is going to happen unless, somehow or another, an incident gets out of hand," Corker said. "But certainly, us showing strength and togetherness with our allies is very important at this time."
"There's no question that this is a little more bellicose than in the past and no question these tests that have taken place have created a lot of concern," he said.
While saying he didn't think an incident would occur, Corker said the heightened rhetoric means "we've got to figure out a way to de-nuclearize North Korea."
Leaders also must figure out how to get China more actively involved, he said because it is "the only country, at this point, that has the ability, because of the way that North Korea depends upon them, to have the kind of effect that is necessary."
The super-maneuverable fighters -- which can evade radar and air-defense systems -- could be sent in to take out air-defense missiles and radars before bombers target missile launch sites or other targets, The Wall Street Journal said.
They also could be used to escort nuclear-capable B-2 stealth bombers if those jet fighters, designed to penetrate dense anti-aircraft defenses, are used in a strike, it said.
Use of the F-22 in the military training exercises shows that "despite challenges with fiscal constraints," U.S. forces "are battle-ready and trained to employ air power to deter aggression, defend [South Korea] and defeat any attack against the alliance," the U.S. military command said in a statement.