The four, reduced from a longer British list, are one Sudanese government official, one pro-government militia member and two rebel leaders, UN diplomats said.

John Bolton, the US ambassador to the UN, told reporters on Wednesday that a 48-hour silence procedure kicked in to secure required unanimous approval by all 15 council members of the list of four deemed to be impeding the peace process and violating international human rights law.

The list was submitted more than a year after the council adopted Resolution 1591, which authorises measures against people committing atrocities or undermining peace efforts in Sudan's western region.

Bolton said the fact that only four people were named did not mean that others would not be considered. "The investigation and consideration of other individuals continue," he said.

Genocide

Britain's UN envoy Emyr Jones Parry called Tuesday's move "the start of a process".

"I joined with the representative of a bigger country, the  United States, in putting forward today four names representing a balanced package and it will be our intention to recommend to our colleagues that sanction measures should be taken against the four  listed," Parry said.

The sanctions involve an assets freeze and travel restrictions on the four for their alleged role in the Darfur violence, which Washington calls genocide.

"The US strongly believes the time has come to designate individuals under UN Security Council Resolution 1591 for targeted sanctions," State Department spokesman Sean McCormack said in Washington.

"The activation of targeted sanctions ... continues efforts to end impunity and is a down payment toward justice and accountability," he told the department's daily briefing.

"I would emphasise the fact that we are looking at individuals from all sectors, including from the government," McCormack said. "We think that this is important."

The council's sanctions committee has been working for weeks on a list of Sudanese to punish for the Darfur conflict, which has killed up to 300,000 people and displaced two million.