U.S President Barack Obama announced a freeze Friday on new offshore oil drilling leases until a review of the accident that caused a massive oil spill in the Gulf of Mexico is done and new safety measures are in place.

U.S. President Barack Obama talks to reporters Friday on the White House lawn about the Gulf of Mexico oil spill. (Evan Vucci/Associated Press)Obama stressed the spill will not derail new drilling entirely.

"I continue to believe that domestic oil production is an important part of our overall strategy for energy security, but I've always said it must be done responsibly for the safety of our workers and our environment," Obama said at a news briefing on the White House lawn.

The spill began after a huge oil rig exploded on April 20 and then sank, breaking from an oil well on the seabed 1,500 metres below.

Oil is gushing from the well, about 80 kilometres off the coast of Louisiana, at a rate of up to 800,000 litres, or 5,000 barrels, a day and neither the U.S. Coast Guard nor oil giant BP are predicting when it might stop.

Obama has ordered Interior Secretary Ken Salazar to review what happened and report back within 30 days, examining what safeguards should be put in place to prevent future spills.

"No domestic drilling in new areas is going to move forward until there is an adequate review of what's happened here and of what is being proposed elsewhere," presidential adviser David Axelrod told ABC's Good Morning America.

In March, Obama announced plans to expand offshore gas and oil exploration off the East Coast and the Gulf of Mexico, a move he hoped would help wean the U.S. from its dependence on foreign oil and strengthen its economy.

"All the president has said is he's not going to continue a moratorium on drilling," Axelrod stressed Friday, when asked if the current crisis was reason to question the president's policies.

Florida's Republican Gov. Charlie Crist, who surveyed the massive oil slick this week and called it "frightening," backed off his support for offshore oil extraction.

"It's the last thing in the world I would want to see happen in our beautiful state," said Crist, adding there is no question now that legislators should give up on the idea this year and in coming years. "Until you actually see it, I don't know how you can comprehend and appreciate the sheer magnitude of that thing."

Congressman John Garamendi, a Democrat from California, said the Gulf spill "marks a turning point in our national discussion on new offshore oil drilling. Those calling for 'Drill, Baby, Drill,' need to start including the corollary, 'Spill, Baby, Spill.'"

Some environmentalists are already mobilizing around the issue.

"This event is a game changer, and the consequences, I believe, will be long-lasting ecologically and politically — and will be irreversible," said Richard Charter, energy consultant for Defenders of Wildlife.

Defends speed of response

Obama seemed to deflect criticism that his administration waited too long to respond to the oil spill, saying his officials have "been working closely with state and local authorities since the date of the explosion."

"There are now five staging areas to protect sensitive shorelines, approximately 1,900 federal response personnel … and more than 300 response vessels and aircraft on the scene 24/7," he said.

"This is always the case in Washington," Axelrod told Good Morning America, referring to political speculation about the speed and efficacy of the response.

"The truth of the matter is we had the coast guard on the scene almost immediately after this accident, the deputy secretary of the interior on the ground the next day and we've been co-ordinating closely with the local authorities and responsible party — BP — down there to deal with this from the very beginning."

Coast guard Rear Admiral Sally Brice-O'Hara also defended the government response, saying it had been rapid and sustained and has adapted as the threat has grown.

The coast guard has posted daily updates about the spill operation on its website, as has BP, which is responsible for the cost of the operation.

With files from The Associated Press