Tons of equipment that left the United States on an Air Force transport with a team of cleanup experts headed for Antarctica Thursday to tackle an oil spill that poses a major environmental threat.

The huge C-5 plane was bound for the southern city of Punta Arenas, where its cargo and the 15-member team will be transferred to a U.S. research vessel, the Polar Duke, the U.S. Embassy in Santiago said.In the Antarctic, U.S. scientists were trying to catch floating oil barrels and propane containers near the spill, which was four miles in diameter and moving to the southwest, the National Science Foundation said.

The agency said in Washington that the Argentine supply vessel that released the oil after it ran aground and sank had carried 250,000 gallons of diesel fuel. It said an "incurable disaster" would result if all the fuel leaks into the pristine region's unspoiled waters.

In Buenos Aires, an Argentine navy spokesman insisted that the spill was not posing a serious ecological threat.

The Bahia Paraiso (Paradise Bay) ran aground Saturday in the Bismarck Strait, about 600 miles south of the southern tip of South America and 11/2 miles from the U.S. Palmer Research Station on the Antarctic Peninsula.

All passengers and crew were rescued, but the ship floated free in heavy seas and sank Tuesday, spilling barrels of oil and several hundred propane gas containers, said Jack Talmadge, a spokesman for the National Science Foundation. Another foundation spokesman in Washington, Jack Renerie, said most of the oil was in steel drums so the ecological threat may not be as big as originally feared.

However, "There's a bunch of free (drifting) oil down there," he said. "The slick has arrived at Palmer Station," a scientific outpose run by the foundation.

Talmadge said he was not sure if the oil leak was continuing.

"The water surrounding the ship is covered with a couple of centimeters (about an inch) of oil. There is a sheen of oil in a much wider area around the ship, including evidence of oil on the coastline of the several islands there."

"Wildlife has already begun to be affected," including krill, the small crustaceans that form the basis of the Antarctic food chain, Talmadge said.