North Korea said on Sunday it was ready to sink a U.S. aircraft carrier to demonstrate its military might, as two Japanese navy ships joined a U.S. carrier group for exercises in the western Pacific.

U.S. President Donald Trump ordered the USS Carl Vinson carrier strike group to sail to waters off the Korean peninsula in response to rising tension over the North’s nuclear and missile tests, and its threats to attack the United States and its Asian allies.

The United States has not specified where the carrier strike group is as it approaches the area. U.S. Vice President Mike Pence said on Saturday it would arrive “within days” but gave no other details.

North Korea remained defiant.

“Our revolutionary forces are combat-ready to sink a U.S. nuclear powered aircraft carrier with a single strike,” the Rodong Sinmun, the newspaper of the North’s ruling Workers’ Party, said in a commentary.

The paper likened the aircraft carrier to a “gross animal” and said a strike on it would be “an actual example to show our military’s force.”

We’re getting closer to a real crisis with North Korea, retired US Army colonel says

The United States is trying hard to get China to engage in talks with North Korea, but that probably won’t happen until North Korea agrees to suspend its nuclear program, retired U.S. Army Colonel Jack Jacobs told CNBC on Monday.

“We’re getting closer and closer to a real crisis and that’s because for decades we ignored the problem,” the Medal of Honor recipient said in an interview with “Closing Bell.”

On Monday, Vice President Mike Pence said the “era of strategic patience” with North Korea was over.

“Just in the past two weeks, the world witnessed the strength and resolve of our new president in actions taken in Syria and Afghanistan,” Pence said. “North Korea would do well not to test his resolve or the strength of the armed forces of the United States in this region.”

Tensions have been escalating following repeated North Korean missile tests and concerns that it may soon conduct a sixth nuclear bomb test in defiance of U.N. sanctions.

Former Defense Secretary William Cohen, meanwhile, thinks China is dragging its feet when it comes negotiating with North Korea. He said the country doesn’t want to see a unified Korea with military presence on its border.

However, “that’s something that you can sit down and work out if the Chinese are willing to put the kind of pressure that needs to be put on the North Koreans,” he told “Closing Bell.”

Cohen thinks it is in China’s long-term interest to have a unified, demilitarized Korea, especially with South Korea being one of China’s biggest trading partners.

That said, he doesn’t see that happening in the short term.

“The North Korean regime is a criminal enterprise. They are extortionists. They are saying feed me, fuel me, employ me before I test again or kill again,” he said.

“That has reached a point where this administration has said, ‘We’re not going to play that game anymore,’ and so we’re asking China to really have an impact in terms of what food and fuel and employment their providing to the North Koreans,” he added.

Jacobs agreed that unification may be a long-term outcome but said the first step needs to be getting rid of the nuclear weapons.

“We have to remember the North Korean government is a continuing criminal enterprise. The thing they fear the most is not being in power. China is very much concerned with destabilization of Korean peninsula. That comes with the North Korean’s government falling to pieces under pressure from anybody.”