The federal government's point man on the Gulf of Mexico spill response said Wednesday there is no "significant risk" that more oil will leak into the sea when engineers remove the temporary cap Thursday that first contained the gusher in mid-July.

Retired Coast Guard Adm. Thad Allen said vessels will remain on standby just in case to collect any leaking oil.

"We do believe the risks are small for any hydrocarbon release," Allen said during a teleconference he held from BP's U.S. offices in Houston, where he met with BP engineers and senior leaders.

But he warned that with the cap and blowout preventer removed, engineers will be relying on the strength of the plug created when cement was pumped in from the top of the well.

"The goal there will be to secure the annulus as quick as we can," Allen said.

Allen said a break in the weather was expected in the Thursday-Friday timeframe, allowing engineers to proceed with the removal of the cap and then the raising of the blowout preventer, which failed to stop the oil from leaking in the first place.

That means the blowout preventer could begin being raised late Thursday or early Friday, but Allen cautioned that timeline could be stretched again if high seas continue to kick up.

After the failed blowout preventer has been removed and replaced with another one, engineers will then proceed with the final plugging of the blown-out well from the bottom using a relief well that has been drilled beside the well that blew out.

Government investigators are waiting to take possession of the failed blowout preventer, which is a key piece of evidence in ongoing probes of the disaster.

Allen said Wednesday that engineers don't currently know the exact condition of the 50-foot, 300-ton device.

"We will not know the exact status until they get that thing ashore and look inside," Allen said.

The Deepwater Horizon explosion April 20 killed 11 workers and led to 206 million gallons of oil spewing from BP's undersea well.

Meanwhile, BP PLC said it has spent more than $5 million a week on advertising since the Gulf oil spill began — more than three times the amount it spent on ads during the same period last year.

BP told the House Energy and Commerce Committee that it spent a total of $93 million on advertising from April to the end of July. The company says the money was intended to keep Gulf Coast residents informed on issues related to the oil spill and to ensure transparency about its actions. The increased spending was largely targeted at TV, newspapers and magazines. A small portion was directed to the Internet.

BP said it actually aired fewer TV spots from April to July than during a similar period last year.