North Korea stepped up its defiant rhetoric against the U.S. on Friday and said the U.S. is making “criminal moves for igniting a war of aggression,” according to a state-run outlet.

The communist state also chided calls for negotiations for denuclearization and again slammed President Donald Trump for seeking “extinction” of North Korea through “pressures and sanctioning,” said the propaganda site DPRK Today.

On Friday, Defense Secretary James Mattis, in remarks at heavily fortified Demilitarized Zone border, said “our goal is not war, but rather the complete, verifiable and irreversible denuclearization of the Korean Peninsula.” He also reiterated America’s “ironclad commitment to the South Korean people.”

The Navy has three carrier strike groups currently operating in the 7th Fleet region but they are not currently all in the western Pacific. The 7th Fleet region includes both the Indian and Pacific Oceans.

The current show of force in Asia waters comes just before an upcoming state visit to South Korea by Trump.

“Everybody is concerned we’re posturing to go to war but I don’t see that,” said David Maxwell, associate director of Georgetown University’s Center for Security Studies. “I think it’s important that we continue to demonstrate that we have the will and capability should North Korea conduct any kind of attack against our ally in the South.”

Defense experts say the carrier-based aircraft has the ability to perform a preemptive strike against North Korea and fleet escort ships could fire cruise missiles. The North’s new air-defense system, though, might be capable of intercepting the military aircraft and missiles.

“This gives us the ability to actually do something as opposed to other kinds of military-symbolic gestures,” said Denny Roy, an Asia Pacific security expert and senior fellow at the East-West Center, a think tank in Honolulu. In the past, he said, the U.S. has tended to use symbolic flights of aircraft along the border or send a single ship near North Korea.

However, even the carriers would not be enough firepower to defeat Pyongyang if there was a full-scale war in Korea.

Maxwell, a retired Army Special Forces colonel, said the carrier strike groups “bring tremendous capability but not enough to win the war. To win the war, it’s going to take the deployment of ground forces, and of course the complete mobilization of the [Republic of Korea] military.”

The carrier battle groups in Asian waters comes as the Pentagon’s top general — Marine Corps Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff — is in South Korea to meet with leaders of South Korea’s military “to examine strategies, plans and means needed to deter any North Korean aggression,” according to the Department of Defense.

Asked by reporters traveling with him about the three nuclear-powered carriers in Asian waters — the USS Nimitz, the USS Reagan, the USS Theodore Roosevelt — Dunford said it was coincidental.

Regardless, experts see a risk still of a catastrophic misunderstanding given the tensions. North Korean leader Kim Jong Un is also a wild card because he might pull the trigger first if he believes the U.S. is about to strike his regime.

“Miscalculation could come from how does North Korea interpret three carrier strike groups in the region,” said Anthony Ruggiero, a senior fellow at the Foundation for Defense of Democracies, a Washington think tank.

Even so, Ruggiero said he was encouraged by recent comment from Secretary of State Rex Tillerson that there are several avenues for diplomatic talks. “One of those channels could be used to de-escalate something that could escalate into a conflict,” he said.

Data from the Center for Strategic and International Studies on North Korean missile launches and provocations shows the months of November, December and early January “tend to be more quiet,” said Lisa Collins, fellow with the Korea Chair at CSIS, a Washington think tank. She explained that the country’s cold weather can create technical problems during missile launches.

Collins said that pattern of decreased provocations could create an opportunity for “more exchanges of dialogue or reaches out to North Korea through back channels.” (She added that she doesn’t have firsthand information on whether it’s happening now.)

Still, Reuters reported Wednesday a North Korean diplomat repeated the dynastic regime’s threat to conduct an atmospheric hydrogen bomb test over the Pacific.

“Are they serious about it — in my personal opinion yes,” said Dean Cheng, a defense expert and senior research fellow at the Heritage Foundation, a Washington-based conservative think tank. He said the last few underground nuclear tests by Pyongyang have been greeted by Washington and international officials with “open skepticism about whether or not it’s a hydrogen bomb.”

To prove he has the superbomb, the North Korean leader will “do an open air test and then there won’t be any questions,” Cheng said.