BP began its most ambitious attempt to plug a more than monthlong leak from an oil well in the Gulf of Mexico.

BP is aiming to tamp down the gusher of oil and natural gas with mud-like drilling fluid, then seal the well with cement. Success would bring to an end a leak that has poured millions of gallons of oil into the Gulf and soiled at least 70 miles (113 kilometers) of coastline.

The so-called top kill process might take two days to complete, Chief Executive Officer Tony Hayward said this morning on NBC’s “Today” show. Hayward put the chances of success at 60 percent to 70 percent two days ago.

The well, about 40 miles off Louisiana’s coast, began leaking after an April 20 explosion and fire on the Deepwater Horizon drilling rig. BP, based in London, leased the rig from Geneva-based Transocean Ltd., the largest deepwater driller.

BP is “in the position of a surgeon about to operate on one of your loved ones,” Gene Grabowski, chairman of the crisis and litigation practice at Levick Strategic Communications, a public relations firm in Washington, said today in an interview.

“Once they cap the well, a level of anxiety will still be there but it will go down precipitously,” he said. “The healing can proceed and they can start talking about what they’re doing to clean up the environment and what the road ahead looks like.”

The spill has cost BP $760 million, or about $22 million a day, the company said May 24. Average daily profit last year was $45 million a day, according to company reports compiled by Bloomberg News.

Federal officials yesterday expanded fisheries closures to encompass about 22 percent of the Gulf of Mexico, or 54,096 square miles, idling commercial and recreational fishing boats.

President Barack Obama plans to visit the region on May 28 and outline new safety measures for offshore drilling.

After receiving an initial report tomorrow on the cause of the explosion, Obama will respond with new permitting procedures for oil exploration and tougher inspections to ensure safety and environmental rules are being followed, according to an administration official who asked not to be identified before the announcement.

(Source: Bloomberg News)