The United States is considering all its options against North Korea after the communist state's sixth, most powerful nuclear test -- a hydrogen bomb this time -- has deepened tensions.
The White House held a national-security briefing involving President Donald Trump, Vice President Mike Pence, Defence Secretary James Mattis and top national-security advisers.
General Mattis says the President has been informed about the military's possible next steps against North Korea.
"We made clear that we have the ability to defend ourselves and our allies South Korea and Japan from any attack, and our commitments among the allies are ironclad. Any threat to the United States or its territories, including Guam, or our allies, will be met with a massive military response, a response both effective and overwhelming."
North Korea has repeatedly defied United Nations sanctions and international pressure by developing nuclear weapons and missiles that could potentially reach the United States.
The UN Security Council has scheduled another emergency meeting to discuss an international response.
General Mattis says he hopes North Korean leader Kim Jong-un will consider denuclearisation.
"Kim Jong-un should take heed of the United Nations Security Council's unified voice. All members unanimously agreed on the threat North Korea poses. And they remain unanimous in their commitment to the denuclearisation of the Korean Peninsula, because we are not looking to the total annihilation of a country -- namely, North Korea -- but, as I said, we have many options to do so."
President Donald Trump has strongly condemned North Korea's actions, calling them "very hostile and dangerous."
He put North Korea's trading partners on notice, warning the United States may stop trading with any country doing business with the North Koreans.
If carried out, that could mean a halt to US trade with China, which has supported economic sanctions on North Korea but remains its key economic partner.
US treasury secretary Steven Mnuchin has confirmed on Fox News he is compiling a new sanctions package to potentially cut off all trade with North Korea.
"I'm going to draft a sanctions package to send to the President for his strong consideration that anybody who wants to do trade or business with them would be prevented from doing trade or business with us. We are going to work with our allies, we'll work with China, but people need to cut off North Korea economically. This is unacceptable behaviour."
In Australia, Prime Minister Malcolm Turnbull has also emphasised the need to cut economic ties with North Korea.
He has told the ABC China has the leverage to lower the tension.
"Unless the regime changes its mind, that will require stronger economic pressure on North Korea. The country that has the ability to impose that pressure is China. China has the overwhelmingly dominant economic relationship with North Korea -- it's its neighbour, of course -- and China can do more."
Foreign Minister Julie Bishop has told Channel Seven, if China cut oil supplies to North Korea, it would have a significant impact on the country.
"An unprecedented pressure will have to be brought to bear on North Korea to make it change its behaviour. It is possible to deter North Korea, so we urge all countries that are trading with North Korea to cease doing so, because we've got to prevent it receiving the finance that it's using to fund these illegal ballistic-missile and nuclear tests."
