The US government allowed the cap stemming the flow of oil in the Gulf of Mexico to remain closed on Monday for another day.
US disaster response commander Admiral Thad Allen said seepage and other anomalies had been found close to the blown-out well but none consequential enough to stop the well integrity test, now in its fifth day.
"We have agreed that we will go forward with another 24-hour period," he said.
Despite his optimism, AFP reports, Admiral Allen ordered BP to produce a "detailed timeline" by the end of Monday for restarting operations to contain the oil with a fleet of surface vessels if the cap had to be opened again.
The announcement last Thursday that BP had stopped the oil flow completely for the first time since April raised hope along the Gulf Coast that a three-month nightmare may soon be over.
'Static kill' idea floated
Measuring devices on BP's cap have given steadily increasing high-pressure readings, which would indicate there are no major leaks in the well bore that stretches an astonishing four kilometres below the seabed.
Both Admiral Allen and BP are floating the idea of a new operation to plug the well called the "static kill" - very much like the "top kill" operation that failed almost two months ago.
BP says the idea would be to send down heavy drilling mud through the giant blowout preventer valve that sits on top on of the well and then inject cement to seal it.