Spill response training efforts are continuing as both professionals and volunteers work to tackle the Deepwater Horizon oil spill, which has now surpassed the Exxon Valdez disaster as America's largest oil spill, according to official figures.

Data from US Geological Survey showed that at least 260,000 barrels of oil had spilled into the Gulf of Mexico by May 17th, exceeding the 257,000 barrels that affected the Prince William Sound in Alaska after the Valdez tanker ran aground in 1989.

The director of US Geological Survey Marcia McNutt told Reuters: "This is obviously a very, very significant environmental disaster and I think with the numbers I've given you, you can do the math."

To tackle the spill, BP yesterday began a "top kill" solution which involves pumping drilling fluid into the well and sealing it in cement.

Progress will be keenly watched by President Obama, who is coming under increasing pressure to show strong leadership in his handling of the crisis.

Oil and Gas Directory: Training and Development