U.S. President Donald Trump vowed on Thursday to confront North Korea "very strongly" following its latest missile test and urged nations to show Pyongyang there would be consequences for its weapons programme.

North Korea on Tuesday test launched an intercontinental ballistic missile that some experts believe has the range to reach Alaska and Hawaii and perhaps the U.S. Pacific Northwest. North Korea said it could carry a large nuclear warhead.

Speaking at a news conference with Polish President Andrzej Duda, Trump said North Korea was "a threat, and we will confront it very strongly".

He said the United States was considering "severe things" for North Korea, but that he would not draw a "red line" of the kind that his predecessor, Barack Obama, had drawn but not enforced on the use of chemical weapons in Syria.

Trump added: "They are behaving in a very, very dangerous manner and something will have to be done."

U.S. Defense Secretary Jim Mattis said the missile test in itself did not bring the parties closer to a war and stressed that America's focus was on diplomatic efforts to pressure Pyongyang.

"We stand ready to provide (military) options if they are necessary. But this is a purely diplomatically led (effort)," Mattis told a small group of reporters at the Pentagon.

"Diplomacy has not failed. ... Diplomatic efforts remain under way as we speak."

Mattis spoke by phone with South Korean Defence Minister Han Min-koo on Thursday, reaffirming Washington's commitment to the U.S.-South Korea alliance and promising "the full range of U.S. capabilities." He spoke with his Japanese counterpart on Wednesday.

The issue presents Trump, who took office in January, with perhaps his biggest foreign policy challenge and has put pressure on his relationship with Chinese President Xi Jinping, whom the Republican president had pressed without success to rein in Pyongyang.

China called on Thursday for restraint and made clear it did not want to be targeted by U.S. sanctions.

Chinese Vice Finance Minister Zhu Guangyao said that while China would implement relevant U.N. resolutions, "the U.S. should not use their domestic laws as excuses to levy sanctions against Chinese financial institutions".

Late on Thursday, court filings made public disclosed that U.S. authorities were trying to seize millions of dollars from companies that deal with North Korea, including the country's military, from eight large international banks.

Russia objected on Thursday to U.N. Security Council condemnation of the North Korean rocket launch because the U.S.-drafted statement referred to it as an intercontinental ballistic missile, diplomats said.

Moscow has said it believes Pyongyang fired an intermediate-range ballistic missile on Tuesday, while China has not identified the rocket launched. North Korea said it tested an ICBM and the United States said that was likely true.

'BAD BEHAVIOUR'

Trump flew to Hamburg on Thursday to attend a summit of leaders of the Group of 20 developed nations, and was due to meet with Xi there.

His frustration that Beijing has not done more to clamp down on North Korea prompted him to tweet on Wednesday: "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!"

Trump did not mention China in his remarks in Poland but his message that other countries needed to do more was clearly meant for Beijing.

"President Duda and I call on all nations to confront this global threat and publicly demonstrate to North Korea that there are consequences for their very, very bad behaviour," he said.

U.S. Ambassador to the United Nations Nikki Haley told the U.N. Security Council on Wednesday the United States would propose new U.N. sanctions in coming days, and that if Russia and China did not support the move, then "we will go our own path."

Some diplomats say Beijing has not been fully enforcing existing international sanctions on its neighbour and has resisted tougher measures, such as an oil embargo, bans on the North Korean airline and guest workers, and measures against Chinese banks and other firms doing business with the North.

U.S. officials have said the United States might seek unilaterally to sanction more Chinese companies that do business with North Korea, especially banks, echoing a tactic it used to pressure Iran to curb its nuclear programme.