The US is "totally prepared" to use a military option to deal with the threat from North Korea, President Donald Trump has said.
"It will be devastating," he warned.
A military option is not the preferred one, but Mr Trump added: "If we have to take it, we will."
The president was responding to comments from North Korea’s foreign minister, who on Monday said that Mr Trump’s recent threatening statements toward the North were a declaration of war and it would have the right to shoot down US war planes.
Mr Trump accused the North Korean leader Kim Jong Un of behaving "very badly".
He blamed previous US presidents for failing to deal with the North Korean threat, declaring: "I will fix this mess."
At a White House news conference, Mr Trump also called on all nations "to join forces to isolate the North Korean menace".
He said they must act now to achieve the denuclearisation of North Korea.
The Trump administration has announced new sanctions which punish eight North Korean banks and 26 bank workers living abroad.
The sanctions rely on an executive order Mr Trump signed last week to target North Korea’s access to the international banking system.
They come as the United Nations has also recently passed its toughest sanctions package targeting North Korea.
The eight banks are all in North Korea. The Treasury Department said the 26 individuals are North Korean nationals employed by those banks who work in Russia, China, Libya and the United Arab Emirates.
Treasury Secretary Steven Mnuchin said the US is targeting those "across the globe" who facilitate financial transactions for North Korea. He said it is part of the effort to isolate North Korea over its nuclear weapons program.