The United States is certain it can defend itself from an attack by North Korea, the Defense Department said Tuesday after Pyongyang warned it was close to test launching a ballistic missile.

"We remain confident in our ballistic missile defense and in our defense of our allies and our defense of the homeland," Pentagon spokesman Peter Cook said at a news briefing.

North Korean leader Kim Jong-Un, in a New Year's speech Sunday, said the country was "in the final stages of test-launching the intercontinental ballistic missile."

In 2016, North Korea conducted two nuclear tests and numerous missile launches last year alone in its quest to develop a nuclear weapons system capable of hitting the US mainland.

"We would once again call on the North Koreans to refrain from provocative actions," Cook said.

Analysts are divided over how close Pyongyang is to realizing its full nuclear ambitions, especially since it has never successfully test-fired an intercontinental ballistic missile (ICBM).

US President-elect Donald Trump, who will take office on January 20, dismissed Pyongyang's missile claims late Monday.

"North Korea just stated that it is in the final stages of developing a nuclear weapon capable of reaching parts of the US," Trump tweeted. "It won't happen!"

North Korea's drive to develop nuclear ballistic missiles capable of striking the United States and its allies has prompted Washington to reinforce its antimissile defenses in the region.

The defense strategy is based notably on the AEGIS system, powerful TPY-2 radars and the antiballistic missile system THAAD that Washington is relocating to South Korea, a move that has provoked China, North Korea's main ally.

The Pentagon spokesman declined to comment to reporters on whether the US had prepared scenarios on deterrent military actions to stop North Korea from developing nuclear missiles.

"We're constantly adjusting to the threat North Korea poses," Cook said.

Pyongyang "has shown disregard to the international community for its international obligations," he said. "And we're watching this very, very carefully."