BP said Sunday it would keep the cap on the ruptured oil well in the Gulf of Mexico as it continued to search for a permanent solution, dpa reported.
The cap - the first successful attempt to stop the catastrophic leak - was put in place late Thursday.
The company said it hopes to use the giant stopper to prevent any more oil from leaking until it plug the spill permanently.
"Nobody wants to see any more oil flowing into the Gulf of Mexico," said Doug Suttles, BP's chief operating officer. "Right now we don't have a target set to reopen the well."
Suttles told a media briefing in Texas that tests on the 4- kilometre-long pipe reaching from the sea floor to the well bottom had produced encouraging signals and would continue indefinitely.
But he warned that if there were problems and the pipe was unable to withstand the pressure then the leak would have to be reopened and the leaking oil pumped into tankers.
"Decisions (on this) must be taken on a day-to-day basis," he said.
More than 8,200 tons of oil had been flowing daily into the Gulf of Mexico since the spill was triggered by an explosion on BP's Deepwater Horizon drilling rig on April 20.
The oil has polluted large stretches of beaches and caused untold hardship to wildlife, fishermen and other people dependent on the tourist industry for a living.
But it remains unclear how things will proceed.
The US government official in charge of the operation, Admiral Thad Allen, had given BP three days to see if its stopgap capping measure works.
He said on Saturday that after the tests were completed the cap would be hooked up to pipes stretching to ships on the surface that will collect the oil.
Experts have voiced fears the pipe inside the well would not bear up to the pressure and could burst.
Suttles said "integrity tests" conducted on the pipes had shown a few bubbles escaping, but this was not a cause for concern. The tests, originally set to last for 48 hours, would continue for longer, he said.
Suttles said the oil giant's goal was to keep the well closed until a permanent solution was in place.
BP is drilling two relief wells, one of which was expected to reach the broken well's casing late July. It then plans to jam the leaking well with mud and cement in August.