BP is trying several new ways to stop the leak from an oil well in the Gulf of Mexico.
The company says it will attempt to place a small containment box over the rupture, after efforts to install a larger device failed. However, it could take another 72 hours to put in place on the seabed.
An earlier attempt with a larger dome failed on Saturday.
The BBC reports the broken pipe is 1.6 km down on the ocean floor with little visibility for engineers using remotely controlled vehicles.
BP has also been making further attempts to thin the leaking oil, by spraying undersea chemical dispersants into it.
Company officials say another option is to try to plug the leak with rubbish.
The well has been leaking since the Deepwater Horizon rig was destroyed in an explosion on 20 April. It sank two days later.
An estimated 5000 barrels (210,000 gallons) of oil per day are flowing into the sea. The slick so far covers about 5200 sq km.
BP says the clean-up cost to date is $US350 million.