WASHINGTON (Reuters) - Thousands of black American farmers denied part of a landmark $2.3 billion civil rights settlement are asking Congress for one more chance at compensation, a farm group said on Tuesday.

John Boyd, president of the National Black Farmers Association, said he met with Democrats on Monday and was "very optimistic" that lawmakers would soon introduce legislation to help black farmers.

In 1999 under the Clinton administration, the federal government agreed to compensate black farmers for decades of racial discrimination that shut them out of billions of dollars in federal subsidies. The U.S. Department of Agriculture agreed to pay at least $50,000 to each eligible black farmer.

However, the USDA rejected payments to 82,000 of the 94,000 black farmers who applied -- or about 87 percent -- because of insufficient documentation and missed filing deadlines, according to a report released on Tuesday by the Environmental Working Group.

The USDA has paid black farmers $800 million of the $2.3 billion settlement, the group said.

"What we concluded is that this entire settlement has been a complete failure at every turn for the farmers," said Arianne Callender, the activist group's general counsel.

"The only place left for the farmers to receive justice is the United States Congress, which should step in and demand USDA pay off these claims and move on," she added.

Both groups criticized the Bush administration, saying it aggressively fought the black farmers' claims. The environmental group said the Justice Department spent 56,000 hours at a cost of $12 million to oppose some of the compensation claims.

"I think its a national disgrace ... for the Bush administration to come into office and put a screeching halt to payments," Boyd said.

The USDA denied any attempt to hinder payments to the farmers. The USDA said a court-appointed arbitrator was responsible for approving and denying each claim.

The court "has said the USDA has done an exemplary job in implementing its part of the consent decree," said USDA spokesman Ed Loyd.

The number of black farmers in the United States has steadily dwindled in the past decades, and they now represent about 1 percent of American growers.