United States president Donald Trump's national security adviser, HR McMaster, says North Korea's latest missile test fits into a pattern of threatening behaviour.
He says the United States is going to rely on key allies in the region, including the Chinese leadership, to take action after reports of the failed missile test.
Mr McMaster says the United States, its allies and China are working together on a range of responses.
"I think it's really the consensus with the President, our key allies in the region -- Japan and South Korea, in particular -- but also the Chinese leadership that this problem is coming to a head and so it's time for us to undertake all actions we can, short of a military option, to try to resolve this peacefully. And so we're going to rely on our allies like we always do, but we're also going to have to rely on Chinese leadership."
Senator John McCain says he agrees China is the key to stopping North Korea launching a nuclear missile.
Speaking on NBC's Meet the Press in the United States, he said North Korea continues to make progress in building an offensive weapon despite the failed test.
Senator McCain says action is crucial because North Korean leader Kim Jong-un lacks the restraint of his forebears.
"This is really very serious. This guy in North Korea is not rational. His father and grandfather were much more rational than he is."
Senator McCain says he believes China has the power to destabilise North Korea's nuclear ambitions.
"China is the key. They can stop this if they want to, because of their control over the North Korean economy. And, by the way, I would point out -- and I know this will come up later on, but -- there are artillery (sites) on the border between North and South Korea that can reach Seoul, and we can't take them all out before ... This is very serious. This may be the first test of this presidency. But China can shut them down, and we should be -- whether they're currency manipulators or not -- we should expect them to act to prevent what could be a cataclysmic event."
The Trump administration is focusing its North Korea strategy on tougher economic sanctions, possibly including an oil embargo.
They could also include a global ban on North Korea's airline, intercepting cargo ships and punishing Chinese banks doing business with North Korea.
Visiting South Korea over the weekend, US vice president Mike Pence has told US servicemen and women the US commitment to its alliance with South Korea has never been stronger.
Mr Pence says freedom will prevail.
"This is a challenging time, all over the world but especially here in the Asia-Pacific. The opportunity for me to be here today at such a time as this is a great privilege for me. But let me assure you, under President Trump's leadership, our resolve has never been stronger. Our commitment to this historic alliance with the courageous people of South Korea has never been stronger, and, with your help, and with God's help, freedom will ever prevail on this peninsula."
Tensions have risen since President Trump began taking a hard rhetorical line with Kim Jong-un.
The North Korean leader has ignored admonitions from China and has proceeded with nuclear and missile programs the United States sees as a direct threat.
