The UN Security Council was expected to approve on Wednesday a new raft of tough sanctions on North Korea to punish the reclusive regime after its fourth nuclear test and rocket launch.

The council is due to vote on a US-drafted resolution, backed by China, that takes aim at North Korea's banned nuclear and ballistic missile programs by cutting off sources of hard currency and access to material.

The new sanctions come in response to North Korea's fourth nuclear test on January 6 and the launch of a satellite-bearing rocket on February 7 that the world viewed as a disguised ballistic missile test.

The United States has described the package of measures as the toughest yet to hit North Korea, but the impact will largely depend on how China, Pyongyang's sole ally and main benefactor, implements the sanctions.

The resolution would require countries to take the unprecedented step of inspecting all cargo to and from North Korea, impose trade restrictions and bar vessels suspected of carrying illegal goods for North Korea from ports.

It also provides for a ban on exports of coal, iron and iron ore, gold, titanium and rare earth minerals from North Korea, and prohibits the supply of aviation fuel including rocket fuel to the reclusive country.

Banking restrictions would be tightened and governments would be required to ban flights of any plane suspected of carrying contraband destined for North Korea.

Under the measure, UN member states would expel North Korean diplomats engaged in smuggling or other illegal activities.

Luxury watches, snowmobiles, recreational watercraft such as Sea-Doos and sports equipment would be banned from sale to North Korea, building on a previous resolution targeting Pyongyang's elites.

The council had initially planned to vote on Tuesday, but the meeting was delayed at Russia's request to allow for more time to review the text.

Diplomats said they expected Russia to back the measure following what Japanese Ambassador Motohide Yoshikawa said were "minor technical changes" to the draft resolution.

One of those changes involved dropping North Korea's mining development representative in Russia from the new UN sanctions blacklist, according to a revised annex to the draft text seen by AFP.

The annex lists 16 individuals and 12 entities to be hit by an assets freeze and travel ban, including North Korea's NADA space agency and its spy agency, the Reconnaissance General Bureau.

- A shift from China? -

It took seven weeks of tough negotiations for the United States and China to come to agreement on the package of measures.

Japan and South Korea also lobbied for sanctions that they insisted would be significantly stronger than those in place since 2006.

China had maintained that the new resolution should not push Pyongyang toward more erratic and dangerous behavior.

Beijing fears too much pressure could trigger the collapse of the pariah regime, creating chaos on its border.

Talks on ramping up sanctions were held as South Korea and the United States announced plans for the deployment of a new missile defense system on the Korean peninsula and the adoption of new US sanctions against Pyongyang.

"The United States, South Korea and Japan have stopped outsourcing to China their policy on North Korea," said Roberta Cohen, an expert on North Korea at the Brookings Institution.

China, and to a lesser extent Russia, "will find loopholes, they always have," to avoid fully implementing UN sanctions, said Cohen.

But Beijing "sees the mobilization of alliances, strong military alliances between the United States, South Korea and Japan and it sees that it can't go on the way it has," she added.

Taking a hard line, South Korean President Park Geun-Hye said North Korea must pay the price for its latest nuclear test and rocket launch.

"If we leave them alone, they will continue," she said.

The latest resolution would be the fifth set of UN sanctions to hit North Korea since it first tested an atomic device in 2006.