To punish N Korea, US weighs sanctions on Chinese companies

It's an approach that's paid off for the US in the past, including with Iran. So-called secondary sanctions upped the economic pressure on Tehran and helped drive it to the nuclear negotiating table.

There are significant risks, too, however. They include opening a new rift with Beijing that could complicate other US diplomatic efforts. Washington already has sanctions on North Korean companies and people accused of illicit dealings with the North. Secondary sanctions would target banks and companies that do legitimate business with North Korea.

Donald Trump has said he is considering some "very severe things" in response to North Korea's successful test of an intercontinental ballistic missile (ICBM) this week, as he called on other nations to exert pressure on Pyongyang over its "very bad behaviour".

The president's comments, made in Poland, came after the US ambassador to the UN made a push for new sanctions at a security council meeting and said America's "considerable military forces" could be used against North Korea.

Nikki Haley told the meeting the US would submit a draft resolution within days "that raises the international response in a way that is proportionate to North Korea's escalation", but warned Washington had options if diplomacy failed. "The United States is prepared to use the full range of our capabilities to defend ourselves and our allies," Haley said. "One of our capabilities lies with our considerable military forces. We will use them, if we must, but we prefer not to have to go in that direction."

She said the US was eyeing penalties against "any country that does business with this outlaw regime". Trump said the US would confront the North Korean threat, but noted that he would not draw a red line. "I don't like to talk about what I have planned, but I have some pretty severe things that we're thinking about," he said.