Frustrated by a chronic funding gap for the U.N. relief effort in the Darfur region of Sudan, U.N. Secretary General Kofi Annan will issue an urgent appeal Wednesday to wealthy European, Asian and Middle Eastern governments that he believes have been too stingy in addressing the humanitarian crisis, senior U.N. officials said Tuesday.

The move comes as the United States is pressing the U.N. Security Council to adopt a resolution this week imposing an arms embargo against rebels in Darfur and demanding that Sudan disarm, arrest and prosecute Arab militias responsible for killing tens of thousands of black Africans and forcing more than 1 million from their homes. Sudan would have 30 days to satisfy the demands or face possible sanctions under the resolution.

The Bush administration presented the 15-nation council with a new version of the proposed resolution Tuesday. It calls on the United Nations and Sudan to "work closely" to support an "independent investigation" into human rights abuses in Darfur. But the latest draft provided no significant concessions to China, Pakistan and other countries that wanted the United States to drop any reference to possible sanctions against Sudan. U.S. officials charge the Sudanese government has supported the militias, known as the Janjaweed, responsible for most of the violence in Dafur.

Sudan, meanwhile, said Tuesday it would fight any foreign troops sent to Darfur to stop the violence. "If we are attacked, we will not sit silent, we will retaliate . . . but we definitely hope we do not reach that situation," Sudanese Foreign Minister Mustafa Osman Ismail told reporters in Turkey, according to Reuters.

Annan's latest appeal for funding reflects growing frustration as the United Nations has failed to collect even half of the $350 million it requested in March to run its relief operation in Darfur, a violence-torn, impoverished province roughly the size of France. In an effort to reach that goal, Annan will send private letters asking Japan, Germany, France, Spain, Italy and Belgium -- which have provided a total of just over $11.5 million in contributions since March -- to increase their funding for the United Nations' operations.

A senior U.N. official said that contributions from the four richest Gulf states -- Saudi Arabia, Kuwait, Qatar and the United Arab Emirates -- which will also get a plea from Annan, have been "totally insignificant."

"Surprisingly, it's been an uphill struggle to get normally generous donors to wake up to this unfolding catastrophe," said Jan Egeland, the U.N. emergency relief coordinator. "It would be a tragedy if now that we have finally broken down this Berlin Wall created by the Sudanese government around Darfur, we would lack the resources" to address the humanitarian crisis.

Egeland said that the bulk of the U.N. operations have been sustained by the United States, which has underwritten 45 percent of the U.N. budget for the issue, and Britain, the Netherlands and Norway.

U.N. officials have privately voiced exasperation with France and Russia, which rejected a personal request from Egeland for half a dozen helicopters to ferry humanitarian relief supplies to remote parts of Darfur that lack airfields. But they also noted that a group of about 20 traditional donors, including the United States and Japan, failed to respond to a similar request.

European officials called it unfair to accuse them of not giving enough. They say they give generously through private European aid agencies and point out that that the European Union has provided more than $250 million in aid for the Sudan crisis. France's U.N. ambassador, Jean-Marc de La Sabliere, said that, in addition to helping to finance E.U. contributions, France has given about $24 million in direct humanitarian assistance for Sudanese civilians. And on Friday, France and Belgium each offered to underwrite the cost of using one private C-130 transport plane.

Envoys from Islamic and Arab governments, meanwhile, said that their countries are committed to addressing the humanitarian crisis in Sudan but added that some are too poor to give much, and some prefer to give funds directly to governments. "In general, when Arab countries give money it is directly and not through the United Nations," said one senior Arab ambassador, who spoke only on the condition of anonymity. "It doesn't mean that they are not generous."

Pakistan's U.N. ambassador, Munir Akram, said: "I can't speak for other Islamic countries, but we are not a very rich country. . . . We will surely do whatever we can. We are considering what to do."

Displaced Sudanese women line up to receive food at a camp in Kutum.