Donald Trump says the US is fully prepared to take the "military option" to deal with North Korea.
He also blamed past US administrations for failing to resolve the situation on the Korean peninsular and pledged to "fix the mess".
Speaking at a White House press conference, the US President said military action was "not a preferred option" but "if we have to take it, we will".
"If we take that option, it will be devastating, I can tell you that, devastating for North Korea," he said.
"North Korea is a situation that should have been handled 25 years ago, 20 years ago, 15 years ago, 10 years ago and five years ago and it could have been handled much more easily", said Mr Trump.
"You had various administrations, many administrations, which left me a mess. But I'll fix the mess. So we'll see what happens with North Korea."
His comments come after the US sent bomber jets to South Korea over the weekend as tensions between the US and North Korea continue to worsen.
In response North Korea said they had the right to "shoot down" US planes - even if they were not in the country's airspace.
The move was criticised by both Russia and China who said there would be no winners if war broke out on the Korean peninsula.
During the press conference Mr Trump also continued his war of words with North Korean leader Kim Jong Un.
He said the North Korean leader was "acting very badly" and accused him of "saying things that should never ever be said".
The Trump administration had previously announced new sanctions punishing eight North Korean banks and 26 bank workers living abroad.
Further sanctions have also been introduced by the United Nations in an effort to curb the rouge states nuclear missile programme.