Federal officials, worried about a possible anti-American backlash, are seeking to halt plans by a Colorado firm to export hazardous waste to Sierra Leone in return for a payment to that country of up to $25 million.

The State Department, which learned of the plan in October, has sent at least two cables to U.S. officials in Sierra Leone instructing them to inform the government there about the potential dangers from the waste. tOne of the cables warned that the plan could lead Africans to condemn the United States for "dumping its wastes in the black man's backyard."

A number of countries along the coast of West Africa and elsewhere have been approached recently by U.S. firms seeking permission to dump hazardous waste, according to industry sources. The sources said they knew of such proposals in Nigeria, Liberia, Senegal, Sierra Leone and in Chili in South America.

One Philadelphia landfill owner, David Ehrlich, told The Washington Post yesterday that he has obtained permission to dump hazardous material in an African coastal country -- he declined to name the country but said it was not Sierra Leone -- and planned to begin dumping within several months. State Department officials said they were not aware of the plan.

The United States has no policy governing the export of hazardous waste. The Environmental Protection Agency has asked for regulations to require companies exporting hazardous waste to notify federal authorities.

In the Sierra Leone case, Godfrey Harris, a Los Angeles consultant to the Nedlog Technology Group Inc. of Arvada, Colo., said he and Nedlog Vice President James R. Wolfe approached Sierra Leone President Shiaka Stevens this past fall and offered "up to $25 million" for permission to dispose of the waste in Stevens' country.

Harris, a former State Department employe, said in a telephone interview yesterday that the company submitted two memos to Sierra Leone officials outlining the plan. He said Nedlog planned to ship "all forms of hazardous waste except radioactive waste" to the country.

The payment of up to $25 million was offered to Stevens, he said, "in lieu of fees or taxes. It was to be more or less of a license."

Stevens' reaction to the offer, Harris said, "was one of great interest, but also one of mature political caution."

Other western African nations, such as Liberia, have already gone on record as opposing efforts by U.S. firms to transport hazardous waste to the region. However, Harris said Nedlog is negotiating for waste-processing and disposal sites with several other countries, including Chile.

Wolfe said yesterday that his firm is primarily involved in developing technology to recover minerals from mining and smelting waste. He said the Colorado company has been involved in recycling and recovery projects in Missouri and Arizona.

Nedlog was formed three years ago in conjunction with the Roldiva Corp., a Pittsburgh company connected with the Mellon family. Wolfe said the two are no longer connected.

Sierra Leone, said Wolfe, is "just one of a half-dozen countries we are looking at." He said his company plans to export a million tons of hazardous waste annually for processing and dumping abroad. Wolfe said his firm already has contracts for waste recovery and disposal with two U.S. mining firms.

According to Wolfe, the $25 million figure, which was used by Nedlog in its offer to Sierra Leone, was a "maximum figure -- it could run considerably less." Wolfe declined to identify the source of the funding, which was offered to the African country as an advance payment.

Under the plan, Nedlog would ship waste of an undetermined nature to the Sierre Leone port of Pepal, about 30 miles northwest of the capital of Freetown. The port is equipped with unloading facilities and a rail line leading into the interior, he said.

Wolfe said that his firm has been primarily involved with processing western mining waste. But he declined to say what kind of hazardous material it planned to ship to Sierra Leone.

Other waste disposal industry sources said yesterday that the African west coast has become a prime target for disposing of U.S. waste since federal and state regulators have begun to crack down on disposal here.

Several sources cited proposed hazardous waste regulations by the Environmental Protection Agency which require firms seeking permits for hazardous waste disposal to put up multimillion-dollar bonds.

"We are getting ourselves in a bind," said Ehrlich, the Pennsylvania landfill owner. "We are producing millions of gallons of toxic waste, and there is no place left to put it. Everyone either dumps it illegally or stores it waiting for some answer to come along."

Ehrlich said he recently obtained permission from one country along the African west coast, which he declined to identify, to set up a processing and disposal operation for chemical waste from the United States.