The United States has warned that North Korea is "quickly closing off" the prospect of a diplomatic resolution to the crisis provoked by recent missile launches.
The Trump administration has launched a government-wide effort to identify options for confronting Pyongyang following its unprecedented intercontinental ballistic missile (ICBM) launch.
President Donald Trump and other senior officials raised the prospect of punishing countries that trade with North Korea - a threat aimed directly at China, Pyongyang's biggest benefactor.
In a tweet this morning, Mr Trump questioned why the US should continue what he sees as bad trade deals "with countries that do not help us".
Trade between China and North Korea grew almost 40% in the first quarter. So much for China working with us - but we had to give it a try!— Donald J. Trump (@realDonaldTrump) July 5, 2017
At an emergency meeting of the UN Security Council on Wednesday, Nikki Haley, the US ambassador to the UN, called Pyongyang's missile launch "a clear and sharp military escalation".
She warned that "the world has become a more dangerous place" and China has a key role in promoting peace and "preventing a catastrophe".
Ms Haley said the United States does not seek conflict - "in fact we seek to avoid it" - but she said the launch of an ICBM "is a clear and sharp military escalation" and the US is prepared to use its "considerable military forces" to defend itself and its allies "if we must".
"But we prefer not to go in that direction," she said. "We have other methods of addressing those who threaten us, and of addressing those who supply the threats. We have great capabilities in the area of trade."
She said she spoke at length to Mr Trump on Wednesday morning about "countries that are allowing, even encouraging trade with North Korea, in violation of UN Security Council resolutions".
"Such countries would also like to continue their trade arrangements with the United States," she said. "That's not going to happen. Our attitude on trade changes when countries do not take international security threats seriously."
The Security Council has imposed six rounds of increasingly tough sanctions on North Korea to try to rein in its nuclear and ballistic missile programs.
Ms Haley said much of the burden of enforcing them rests with China, which is responsible for 90% of North Korea's trade.
"We will work with China," she said. "We will work with every country that wants peace, but we will not repeat the inadequate approaches of the past that have brought us to this dark day."
Ms Haley said the United States will circulate a new Security Council resolution in the coming days "that raises the international response in a way that is proportionate to North Korea's escalation".