(reuters) -- The Trump administration has repeatedly said all options are on the table in dealing with North Korea's ballistic and nuclear weapons programmes, including military ones, but that it still prefers a diplomatic option.

Speaking at an emergency U.N. Security Council meeting, U.S. ambassador Nikki Haley said the United States had never sought war with North Korea.

"If war does come, it will be because of continued acts of aggression like we witnessed yesterday," she said. "...and if war comes, make no mistake, the North Korean regime will be utterly destroyed."

Haley said the United States has asked China to cut off oil supply to North Korea, a drastic step that Beijing - the North's neighbour and sole major trading partner - has so far refrained from doing. Trump and Chinese President Xi Jinping talked on the phone earlier on Wednesday.

"Just spoke to President Xi Jinping of China concerning the provocative actions of North Korea. Additional major sanctions will be imposed on North Korea today. This situation will be handled!" Trump wrote on Twitter.

Previous U.S. administrations have failed to stop North Korea from developing nuclear weapons and a sophisticated missile programme. Trump, who has previously said the United States would "totally destroy" North Korea if necessary to protect itself and its allies from the nuclear threat, has also struggled to contain Pyongyang since he came to office in January.

Urging China to use its leverage and promising more sanctions against North Korea are two strategies that have borne little fruit so far.

In a speech in Missouri about taxes, Trump, who has traded insults with the North in the past, referred to North Korean leader Kim Jong Un with a derisive nickname.

"Little Rocket Man. He is a sick puppy," Trump said.