Russia has ruled out U.N. Security Council sanctions against Sudan for its failure to control Arab militias in the Darfur region. The senior U.N. envoy to Sudan will brief the Council Thursday on his just-completed trip to investigate reports of continuing atrocities in Darfur. But, Russia's opposition effectively makes sanctions a dead issue.

U.N. envoy to Sudan Jan Pronk was tight-lipped Tuesday as he arrived at New York headquarters to report on his week-long fact-finding mission to Darfur.

"I have drafted my report and have given it to the secretary-general yesterday evening and until Thursday, of course you'll understand I can't say anything substantial," he said.

U.N. diplomats say Mr. Pronk's report paints a mixed picture of conditions in Darfur. It credits the Khartoum government with responding to international concerns about the plight of Darfur's villagers. But it concludes that the government failed to meet its obligations to disarm pro-government Arab militias accused of terrorizing black Africans in the region.

But even before the report's release, Russia's U.N. ambassador, Andrey Denisov, declared sanctions unacceptable.

"I think sanctions [are] not a good choice in this particular situation," he said. "The whole performance in Darfur, Sudan is very far from being satisfactory, but we note some positive changes, very steady, very slow, with some retreats, but anyway, the trend is positive."

A Security Council resolution passed in late July threatened sanctions unless Khartoum took action to control the Arab militia known as Janjaweed. The resolution directed the secretary-general to make a progress report every 30 days.

But as the first 30-day period expired, Ambassador Denisov said sanctions may do more harm than good.

"Sanctions [are] like a surgical instrument, [they] must be used very very carefully, and it is clear that the threat of sanctions being applied may be sometimes more powerful weapon than sanctions itself," he said.

With sanctions effectively ruled out, Security Council members are looking to an expanded African Union observer force to prevent further bloodshed in Darfur. An African Union proposal to increase the size of its force in Darfur from 100,000 to 300,000 has met resistance from Khartoum.

The United Nations describes Darfur as the scene of the world's worst humanitarian crisis. Attacks by the Janjaweed have left much of the region in ruins, leaving 30,000 people dead over the past 18 months, and forcing another 1.2 million to flee their homes.