NEW ORLEANS (AP) _ A company's offer to burn 3,000 tons of New York garbage loaded on a barge in the Gulf of Mexico got a quick thumbs-down from Louisiana's environmental chief.

''The Department of Environmental Quality of the state of Louisiana will not accept garbage from that barge,'' Martha Madden, the state's chief environmental officer, said Tuesday.

Marine Shale Processors of Morgan City had offered to burn the garbage as a public service, said Madden.

At last report the barge was 150 miles out in the Gulf of Mexico, more than 1,400 miles from the garbage's source, Islip, N.Y., she said.

The barge left New York on March 22 and was first turned down by North Carolina, then Alabama, Mississippi and Louisiana.

Lowell Harrelson, a Bay Minette, Ala., contractor, had said he thought he had a valid contract to dump the garbage in a North Carolina landfill, before that state and then others turned the barge away.

Louisiana ordered the barge out of state waters last week, saying a dark brown substance was dripping into the water. Officials also expressed concern that discarded medical supplies in the load might be infectious.

On Friday, the barge turned back toward the United States after Mexico refused to allowing dumping in the state of Campeche or to allow the barge to anchor off its coast.

Belize, a tiny Central American nation nestled between Mexico's Yucatan Peninsula and Guatemala, was mentioned early this week as a possible landing site, but that government also said no.

''The idea of us buying that garbage is laughable,'' said Manuel Romero, Belize's chief information officer, said by telex from the nation's capital, Belmopan.

Robert C. Odle Jr., a Marine Shale lawyer, said in a telephone interview from Washington that the company had volunteered to burn the garbage for free and he hoped state officials would reconsider their rejection of the idea.

''Obviously we're not going to buy it from them,'' he said. ''People pay us to take waste from them. In this case, we're just going to do this as a public service.''

He said the garbage would be burned at 2,300 degrees in its 275-foot-long kiln.

''When it comes out the other end, it's a non-hazardous kind of powder,'' he said. ''The powder can be used for landfill, it can be stored, or whatever.''