The first oil from the Gulf of Mexico spill has entered an ocean current that could take it to Florida and up the east coast of the US, scientists say.
The European Space Agency said satellite images suggested oil could reach the coral reefs of the Florida Keys within six days.
"We have visible proof that at least oil from the surface... has reached the current," said Dr Bertrand Chapron.
Meanwhile, the US said it was having talks with Cuba over the spill.
Observers say the talks demonstrate a concern that the oil may be carried by currents far from the site of the Deep Horizon disaster.
A BP executive said this week that the company had paid out $15m (£10.4m) in claims, much of it to shrimpers and commercial fishermen who have little or no income because of the spill.
Meanwhile, astronauts and cosmonauts aboard the International Space Station have said they could see the oil spill while passing over the Gulf of Mexico.
"It looks very scary," Russian cosmonaut Oleg Kotov told reporters via a video link.
