US and its allies considering options after North Korea's 'provocative' missile launch
The US and Britain have ratcheted up pressure on North Korea after its failed missile launch by warning Pyongyang it must end its "belligerent" behaviour.
US national security adviser, Lieutenant General HR McMaster, said the rogue state's actions "just can't continue".
He commented: "This latest missile test just fits into a pattern of provocative, destabilising, and threatening behaviour on the part of the North Korean regime. I think there is international consensus now, including the Chinese leadership, that this is a situation that just can't continue. And the President has made clear that he will not accept the United States and its allies and partners in the region being under threat from this hostile regime with nuclear weapons. We are working together with our allies and partners, and with the Chinese leadership, to develop a range of options."
US President Donald Trump tweeted: "Our military is building and is rapidly becoming stronger than ever before. Frankly, we have no choice!"
UK foreign secretary Boris Johnson tweeted: "I strongly condemn the latest North Korean missile launch. They must stop these belligerent acts and comply with UN resolutions."
US vice president Mike Pence used an address to American military personnel in South Korea to make it clear Washington would take a tough stance against the regime of Kim Jong Un.
"This morning's provocation is just the latest reminder of the risks each one of you face every day in the defence of the freedom of the people of South Korea and the defence of America in this part of the world.
"But let me assure you, under President Trump's leadership our resolve has never been stronger."
Mr Pence was speaking after American officials said a North Korean medium-range missile exploded seconds after it was launched on Sunday. The as-yet unidentified missile exploded on launch from a base in Sinpo, a city on the country's east coast, said the US.
International concern has been growing over the deteriorating situation, with China expressing fears war could break out "at any moment". On Saturday, the North Korean regime gave a huge show of strength with a parade of military hardware feared to have featured a new type of intercontinental ballistic missile (ICBM).
Despite UN sanctions, North Korea launched a long-range rocket and carried out two nuclear tests in 2016, including its most powerful bomb to date. There has also been a series of tests of shorter and mid-range rockets in recent years, with varying success.
Mr Trump has accused North Korea of "looking for trouble" and has ordered aircraft carrier USS Carl Vinson and several warships to the area.
Choe Ryong Hae, widely regarded as the secretive state's number two leading official, accused Mr Trump of "creating a war situation" by sending American forces to the region.
He said: "We will respond to an all-out war with an all-out war and a nuclear war with our style of a nuclear attack."