Results of a crucial test on BP's well in the Gulf of Mexico are ambiguous and urged BP to increase monitoring during testing, The White House said on Friday.

The New York Times has reported that retired Coast Guard Adm. Thad Allen, overseeing the response to the gulf oil spill, said the testing indicates the well is in good shape, but it was not yet possible to rule out damage that might complicate efforts to permanently stop the leak.

He said, "We want to be careful not to do any harm or create a situation that could not be reversed."

Earlier Friday, President Barack Obama mixed caution with optimism about whether a new containment cap could capture oil spewing into the Gulf of Mexico since April.

Obama said at the White House, "It's important we don't get a head of ourselves here. We're not done."

The cap would give crews "greater control" over the oil flow as relief wells are drilled, he said.

Obama further added that scientists are analyzing data from pressure tests performed on the crippled well to determine "whether we can safely shut in the well ... without creating problems" such as new leaks on the gulf floor.

The president said, "It is our responsibility to make sure we're taking a prudent course of action."

According to him, the good news is that crews will be able to use the cap to stop the flow of oil or capture all of the oil until the relief wells are done.

The new cap will be able to contain up to 80,000 barrels of oil a day and "allow us to capture all of the oil until the well is killed," he said.

He added, "Even if it turns out we can't maintain this cap and shut off flow of oil, it allows us to attach many more containment mechanisms ... so we're able to take more oil up to the surface and it won't be spilling into gulf." (With Inputs from Agencies)