US sanctions-based approach was complemented, rather than undercut, by Beijing's "subtle diplomacy", Andrew Natsios, the US special envoy for Sudan, told a Senate hearing, the report said.

Smoke and flames are seen in Khartoum near the military headquarters in Khartoum, the capital of Sudan after a military truck carrying ammunition exploded as a result of a fire on the vehicle Saturday, April 7, 2007. The blast caused no casualties, the army said. [AP]

"I think they may be the crucial actors. I think there's been a lot of China-bashing in the west. And I'm not sure, to be very frank with you, right now it's very helpful," Mr Natsios was cited as saying.

Mr Natsios said there were signs that China was being more "aggressive" in urging Khartoum to accept a UN peacekeeping force in Darfur, according to the report.

He believed China's diplomacy might have been the "critical factor" that led Sudan to reverse its position in talks this week and accept the "heavy support package" for the African Union mission already in Darfur, the report said.

China has been gradually increasing the pressure on Sudan to accept a U.N. peacekeeping force. Chinese President Hu Jintao told the Sudanese government in February that it must give the U.N. a bigger role in trying to resolve the conflict in Darfur.

Sudan and the United Nations agreed in November on the incremental deployment of a joint African Union-U.N. force of 20,000 peacekeepers in Darfur. But Sudanese President Omar al-Bashir has since backed off, saying he will only accept a larger AU force with technical and logistical U.N. support.

The United Nations says the 7,000-member AU force now on the ground is overwhelmed in Darfur, a region the size of France.

At least 200,000 people have been killed and 2.5 million have been driven from their homes since the conflict there erupted four years ago between ethnic African rebels and the Arab-dominated central government.

Related Readings: Darfur crisis needs world's helping hand China will continue to work on Darfur issueSudan, UN to work for Darfur peace China urges deployment of peace-keeping forces in Darfur China supports consensus on Darfur issue Hu puts forward principle on Darfur issue

Last month, the U.S. government said it was preparing to impose new economic sanctions on Sudanese companies and block international sanctions. Britain has called on the U.N. to consider imposing a no-fly zone over Darfur. The measure apparently would be directed at stopping the Sudanese government's aerial bombardment of rebel positions.

But U.N. Secretary General Ban Ki-moon said last week that talk of sanctions should wait until he has had more time to pressure Sudan diplomatically.