UPDATE 1-North Korea Cannot 'tip' Missile with Nuclear Warhead -U.S. State Dept

(Adds U.S. comment, background)

WASHINGTON, Jan 3 (Reuters) - North Korea continues to pursue nuclear and ballistic missile technologies but the United States does not believe it is in a position to "tip" one of them with a nuclear warhead, State Department spokesman John Kirby said on Tuesday.

North Korea's leader, Kim Jong Un, said on Sunday his nuclear-capable country was close to test-launching an intercontinental ballistic missile (ICBM), raising the prospect of putting parts of the United States within range.

"We do not believe that at this point in time he has the capability to tip one of these with a nuclear warhead ... but we do know that he continues to want to have those capabilities and the programs continue to march in that direction," Kirby told reporters.

Asked whether he would agree with President-elect Donald Trump's assessment that China was not helping to contain North Korea's nuclear ambitions, Kirby said: "We would not agree with that assessment."

Trump, who will take office on Jan. 20, tweeted on Monday that North Korea would not be allowed to complete a nuclear weapon capable of reaching the United States, although he did not say how he would stop it. "It won't happen!" he said on Twitter.

Trump's transition spokesman, Sean Spicer, said the tweet spoke for itself but added that it meant, "Under his watch he's going to make sure that that doesn't happen."

Pyongyang's action will be discussed at a meeting in Washington on Thursday between the United States, Japan and South Korea, led by Deputy Secretary of State Antony Blinken, Kirby said.

"No question that tensions on the Korean peninsula will be a topic of discussion (but) where that is going to take us, especially in light of Kim Jong Un's speech, I don't know," Kirby said.

Asked about the possibility of more sanctions against Pyongyang, he added: "We haven't ruled out the possibility of additional sanctions." (Reporting by Lesley Wroughton; Writing by Doina Chiacu; Editing by James Dalgleish and Alan Crosby)