The United States and China will on Thursday seek to tighten the UN sanctions screws on North Korea after its widely condemned nuclear bomb test last month.

After weeks of closed-door talks, the UN Security Council will vote at 1500 GMT on a resolution proposed by the two key powers that targets North Korean diplomats, finances and access to luxury goods, and blacklists its accused weapons dealers.

A unanimous vote by the 15-member council is certain. "The response by the worryingly unpredictable North Korean government is anyone's guess," said a UN council diplomat.

The North shrugged off sanctions imposed after its nuclear weapons tests in 2006 and 2009 to stage a banned long-range rocket test in December and an even more provocative nuclear blast on February 12.

US ambassador to the United Nations, Susan Rice, vowed this riposte will "take the UN sanctions imposed on North Korea to the next level, breaking new ground and imposing significant new legal obligations."

China is less keen on antagonizing its neighbor. But its UN ambassador, Li Baodong, said "a strong signal must be sent out that the nuclear test is against the will of the international community."

The resolution expresses "gravest concern" over the nuclear test and adds three new individuals, a government science academy and trading company to the UN blacklist for a travel ban and assets freeze.

Yon Chong-Nam and Ko Chol Chae are the head and deputy chief of Korea Mining Development Trading Corporation (KOMID), which the resolution says is North Korea's "primary arms dealer and main exporter of goods and equipment related to ballistic missiles and conventional weapons."

The third individual Mun Chong Chol of Tanchon Commercial Bank which is described as the North's main "financial entity for sales of conventional arms, ballistic missiles" and related goods.

The government's Second Academy of Natural Sciences carries out research on North Korea's "advanced weapons systems, including missiles and probably nuclear weapons," says the draft resolution.

Korea Complex Equipment Import Corporation is a subsidiary of a North Korean conglomerate that buys equipment for the North's defense industries and giant military.

The resolution calls for "enhanced vigilance" over North Korean diplomats. US officials suspect the diplomats have been carrying suitcases of cash to get around financial sanctions.

It says that a ban on financial transactions linked to the North's weapons programs must include "bulk cash" transfers.

Earlier resolutions gave states the right to inspect suspect cargos. Those inspections will become mandatory. The new measures also call on states to turn away airplanes if there are reasons to believe that they carry prohibited items.

The resolution will put Pyongyang under one of the toughest sanctions regimes ever ordered by the United Nations. And the resolution threatens "further significant measures" if the North stages a new nuclear test or rocket launch.

South Korea and Japan support the new sanctions, according to their diplomats.

But the North has already angrily threatened to pull out of an armistice that halted the 1950-1953 Korean War, heightening tensions with its neighbor and the United States.

"If North Korea carries out provocations that threaten the lives and safety of South Koreans, our military will carry out strong and resolute retaliations," South Korea's General Kim Yong-Hyun responded.