BP Plc launched an ambitious deep sea operation to choke off a gushing oil leak in the Gulf of Mexico today, but US president Barack Obama cautioned Americans there was no guarantee it would work.
BP is under intense pressure from Mr Obama to bring a swift end to the five-week-old spill that threatens an environmental catastrophe and has ignited a political storm.
Undersea robots were being used to help inject heavy fluids and ultimately cement pumped down about a 1.6km to the sea-bed well. The so-called "top kill" procedure has never been attempted at such depths.
Mr Obama said if successful, BP's plan to cap the well should greatly reduce or eliminate the flow of hundreds of thousands of litres of crude billowing into the Gulf.
"We will not rest until this well is shut, the environment is repaired and the cleanup is complete," he said on a trip to California.
BP Chief Executive Tony Hayward told the NBC Today show it would take a day or two to determine whether the top kill procedure had worked.
A BP statement said the "top kill" action began this evening. Interior secretary Ken Salazar appeared to have jumped the gun when he told reporters at a congressional hearing about an hour earlier that the process was under way.
The gushing oil leak threatens some of the United States' richest fisheries and has already soiled more than 113 km of Louisiana's 644km coastline.
The US Coast Guard approved the top kill operation, the most ambitious effort to date to cap the well, after government scientists said it was safe to proceed, according to a statement by the oil spill response command centre.
Mr Salazar said he did not know how long it would take BP workers to plug the well. "It depends on what kind of difficulties they encounter as they move forward," he said.
Reuters