North Korea is "skating very close to a dangerous line" with its heated rhetoric and provocative actions, US Defense Secretary Chuck Hagel told reporters Wednesday.

The United States and its allies hoped Pyongyang would tone down its inflammatory language but the American military was prepared for any possibility, Hagel said.

"North Korea ...with its bellicose rhetoric, its actions, has been skating very close to a dangerous line," the Pentagon chief said.

"Our country is fully prepared to deal with any contingency, any action that North Korea may take or any provocation that they may instigate," Hagel added.

The US military's top officer, General Martin Dempsey, told the same press conference that he could not publicly comment on intelligence estimates as to how close North Korea was to placing a nuclear warhead on a missile.

But the four-star general said the United States military was ready for the "worst case" scenario.

"They have conducted two nuclear tests. They have conducted several successful missile launches.

"And in the absence of concrete evidence to the contrary, we have to assume the worst case and that's why we're postured as we are today," said Dempsey, chairman of the US Joint Chiefs of Staff.

The military has deployed US naval ships in the region capable of shooting down incoming missiles and staged a show of force with bomber aircraft in a bid to deter North Korea from launching any attack.

Hagel said the United States and its allies hoped "that that rhetoric be ratcheted down" and Pyongyang will seek to defuse a "combustible situation."

The comments come amid widespread speculation North Korea is poised for a missile launch in defiance of UN Security Council resolutions.

The head of US Pacific Command, Admiral Samuel Locklear, told senators Tuesday that he favored shooting down a North Korean missile only if it threatened the United States or Washington's allies in the region.

Locklear, however, said he was confident the US military would be able to detect quickly where any missile was headed.