Sudan 'resumes bombing in Darfur'

Mr Natsios urged Sudan to stop its campaign and respect a 2004 ceasefire.

He said the bombing was focused on the Jebel Marra region, a stronghold of one of the rebel faction leaders, Abdul Wahid Mohammed Nour.

Some 200,000 people have died in Darfur in the past four years, while 2m have fled their homes, the UN says.

The BBC's Amber Henshaw in Khartoum says no-one was available from the Sudanese government to comment on Mr Natsios' claims.

'Warlordism'

"After a halt in the bombing between the beginning of February and the end of April in 2007, the Sudanese government has resumed bombing in Darfur," Mr Natsios said.

He also accused rebel groups of descending into "criminality and warlordism".

"Some rebel leaders are cynically obstructing the peace process and the United States government is very disturbed by this. It needs to end now," he said.

The US special envoy's comments come as Britain, France and Ghana circulate a draft resolution to the UN security Council for a joint African Union-United Nations peacekeeping operation for Darfur.

The Sudanese government finally agreed to allow a 20,000-strong hybrid force into the region after months of pressure from the international community.

There are also moves to get the government and the rebels back to peace talks in the next few months.

Government officials say they are more than ready for talks.

A widely unpopular peace deal was signed last year by one of the three negotiating factions but the groups have now splintered and many are calling for fresh negotiations.