UNITED NATIONS (REUTERS, AFP) - The United Nations Security Council unanimously stepped up sanctions against North Korea on Monday (Tuesday Sept 12, Singapore time) over the country's sixth and most powerful nuclear test, imposing a ban on the country's textile exports and capping imports of crude oil.

It was the eighth sanctions resolution unanimously adopted by the 15-member council since 2006 over North Korea's ballistic missile and nuclear programmes. The United States watered down an initial tougher draft resolution to win the support of Pyongyang ally China and Russia.

A week ago, US Ambassador to the United Nations Nikki Haley called for the "strongest possible" sanctions on North Korea and had sought an oil embargo on Pyongyang.

On Monday, she said the US was not looking for war with North Korea and that Pyongyang had "not yet passed the point of no return".

"If it agrees to stop its nuclear programme, it can reclaim its future. If it proves it can live in peace, the world will live in peace with it," she told the Security Council after it adopted the new sanctions.

"We are done trying to prod the regime to do the right thing. We are now acting to stop it from having the ability to continue doing the wrong thing. We are doing that by hitting North Korea's ability to fuel and fund its weapons programme. Oil is the lifeblood of North Korea's effort to build and deliver a nuclear weapon. Today's resolution reduces almost 30 per cent of oil provided to North Korea by cutting off over 55 per cent of its gas, diesel, and heavy fuel oil.

"Today's resolution completely bans natural gas and other oil byproducts that could be used as substitutes for the reduced petroleum. This will cut deep,'' Haley said.

"These are by far the strongest measures ever imposed on North Korea. They give us a much better chance to halt the regime's ability to fuel and finance its nuclear and missile programmes. But we all know these steps only work if all nations implement them completely and aggressively."

Haley added that the latest resolution "would not have happened" without the strong relationship that had developed between US President Donald Trump and Chinese President Xi Jinping.

China's UN ambassador Liu Jieyi urged North Korea to "take seriously the expectations and will of the international community" and called on all parties to remain "cool-headed" and not stoke tensions.

In Beijing, a Chinese Foreign Ministry spokesman said on Tuesday that China supported the UN Security Council to take necessary measures regarding North Korea's latest nuclear test on Sept 3 in violation of previous Security Council resolutions.

South Korea's presidential Blue House said on Tuesday it welcomed a new UN Security Council resolution imposing additional sanctions on North Korea over its sixth nuclear test. It said the only way for Pyongyang to escape isolation and economic hardship is to end its nuclear programme.

Japanese Prime Minister Shinzo Abe said on Tuesday that it is important to change North Korea's policy by imposing a higher level of pressure on the country than ever before. North Korea late last month flew an intermediate-range ballistic missile, the Hwasong-12 missile, over Japan in a major escalation of tensions in the region.

A Security Council resolution needs nine votes in favour and no vetoes to pass. In negotiations on the latest resolution, diplomats said Russia had questioned what leverage the Security Council would have left if North Korea continued to conduct nuclear and missile testing.

"This is a compromise in order to get everybody on board," French UN Ambassador Francois Delattre said of the draft ahead of the vote.

Textiles were North Korea's second-biggest export after coal and other minerals in 2016, totaling US$752 million (S$1 billion), according to data from the Korea Trade-Investment Promotion Agency. Nearly 80 per cent of the textile exports went to China.

The resolution imposes a ban on condensates and natural gas liquids, a cap of 2 million barrels a year on refined petroleum products, and a cap on crude oil exports to North Korea at current levels. China supplies most of North Korea's crude.

A US official, familiar with the council negotiations and speaking on condition of anonymity, said North Korea imported some 4.5 million barrels of refined petroleum products annually and 4 million barrels of crude oil.

Trump has vowed not to allow North Korea to develop a nuclear missile capable of hitting the mainland US.

North Korea was condemned globally for its latest nuclear test on Sept 3, which it said was of an advanced hydrogen bomb.

Pyongyang warned the US on Monday that it would pay a "due price" for spearheading efforts on UN sanctions.

"The world will witness how the DPRK tames the US gangsters by taking a series of actions tougher than they have ever envisaged," the foreign ministry said in a statement carried by the official KCNA news agency.

DPRK stands for the North's formal name, the Democratic People's Republic of Korea.

The tensions have weighed on global markets, but there was some relief on Monday among investors that North Korea refrained from conducting another missile test this past weekend to celebrate 69 years since its founding.

European Council on Foreign Relations UN expert Richard Gowan said the US had "rather predictably been mugged by reality" during the most recent negotiations" on sanctions.

He added it was arguable, however, that the high US bar had pushed China and Russia to agree to more limited sanctions "relatively quickly".

"China and Russia were never going to accept the severe package of sanctions tabled by Haley," Gowan aid. "This sort of lengthy, incremental diplomatic bargaining may be the best it can hope for. The alternative is, after all, a slide towards war."

Traditionally, the US has discreetly negotiated with China on any North Korea sanctions before expanding talks to the full council once the five veto powers have agreed. More recently, that has typically taken one to three months.

China supplies most of North Korea's crude. Chinese officials have privately expressed fears that an oil embargo could risk causing massive instability in its neighbour.

Chinese Foreign Ministry spokesman Geng Shuang stressed the need for consensus over North Korea and maintaining peace. "I have said before that China agrees that the UN Security Council should make a further response and necessary actions with respect to North Korea's sixth nuclear test," he told reporters.

Russia and China have been critical that there is too much focus on pressuring North Korea with sanctions and not enough debate about kick-starting talks with Pyongyang