BP last week managed to install a tight-fitting cap onto the well that had been leaking tens of thousands of barrels of oil a day into the ocean for nearly three month. BP and government scientists have been holding a tense vigil ever since to see whether the cap is holding without leaks.
"We continue to be pleased with the progress," said Coast Guard Admiral Thad Allen, who is coordinating the federal government response to the spill.
He approved at least another 24 hours for the cap to remain close.
With the well-head capped, engineers have been scouring the ocean floor for any sign of oil seeping into the ocean from somewhere else. Allen noted some "minor leaks" but insisted that none were "consequential for the response".
"As each day goes along, it gives us more confidence" that the well has been fully sealed, BP Vice President Kent Wells said.
Tuesday marked three months since the BP-leased Deepwater Horizon rig exploded about 70 km off the coast of Louisiana, killing 11 workers. The ensuing oil spill is by far the biggest in US history.
Despite the progress, the well-cap is considered a temporary solution to the leak. BP is drilling relief wells in hopes of permanently sealing off the oil reservoir deep beneath the seabed.
Wells said the first relief well was "exactly where we want it", on schedule to intercept the ruptured well at the end of July and seal it off some time in August.
British Prime Minister David Cameron, who met Tuesday in Washington with President Barack Obama, said he could "completely understand the anger that exists right across America" over the disaster.
"The oil spill in the Gulf of Mexico is a catastrophe for the environment, for the fishing industry, for tourism," he said.
"It is BP's role to cap the leak, to clean up the mess and to pay appropriate compensation. I'm in regular touch with senior management at BP, and the president is too, to make sure that happens."