The first significant quantity of oil to wash ashore from the Deepwater Horizon spill in the Gulf of Mexico has hit parts of the Louisiana coastline.
The state's governor said on Wednesday that a thick layer of oil had coated vegetation in the fragile wetlands of the Mississippi river delta.
"The day that we have all been fearing is upon us today," Bobby Jindal told reporters after a boat tour to the southernmost point of the Mississippi river estuary.
He said he would press the federal government to step up efforts to prevent more oil from coming ashore.
"This wasn't tar balls. This wasn't sheen. This is heavy oil in our wetlands," Jindal said.
"It's already here but we know more is coming."
Previously, officials had been reporting "oil debris" in the form of tar balls, or light surface "sheen" coming ashore in outlying parts of Louisiana, Mississippi and Alabama.
Jindal has now appealed to the US Army Corps of Engineers to issue a permit to allow the construction of 128 km of sand levees to protect the Louisiana coastline from further damage.
That project, which would cost $350 million, has been delayed despite an intense effort by the state officials to comply with the Corps' requirements, Jindal said.
The Louisiana governor's comments came as experts confirmed that a "small portion" of light sheen from the oil slick has already entered a strong ocean current that could sweep the slick towards Florida and Cuba and possibly up the US east coast.
|Scientists warned a powerful current could sweep the oil into Florida's coral reeefs [AFP]
The Loop Current has started dragging leaking crude towards Florida's beaches and fragile coral reefs, threatening to add a far larger dimension to the unfolding environmental disaster.
Scientists laid out a worst-case scenario in which the oceanic conveyor belt would see the first oil wash up in Florida in as little as six days, before carrying it up the east coast and even into the Gulf Stream, the northern hemisphere's most important ocean current system.
The potential damage to the region's teeming and important marine life as well as fragile coastlines could be enormous, experts say.
"The Loop Current is a super-highway carrying babies of a wide array of fishes and other kinds of marine life from their spawning zones to the places where they will ultimately grow up," Doug Rader, chief ocean scientist of the Environmental Defense Fund, told the AFP news agency
"This is the major organising aquatic structure in the Gulf. Everything rides the Loop Current."
The European Space Agency said on Wednesday that its satellites showed oil being pulled into the powerful clockwise-moving current that joins the Gulf Stream.
The National Oceanic and Atmospheric Administration (NOAA), the main US agency monitoring the spill, agreed a small portion of the slick had entered the current "in the form of light to very light sheens".
However, the agency added the oil may never reach Florida and if it does it "would be highly weathered" and evaporation and chemical dispersants could have "significantly" reduced the volume.
BP, the energy giant that has claimed responsibility for the slick, has marked some progress at siphoning some of the oil from the well, which ruptured after an April 20 explosion that killed 11 workers.
The company said it is now siphoning about 3,000 barrels a day of oil, out of what the company estimated was a 5,000 barrels a day gusher.