But Bass is yet to secure a $20m deal with Russian space officials to go ahead with the 28 October flight to the international space station.

Despite Russian warnings that payment deadlines have been missed, Nasa seems optimistic that a deal will be done.

Space flight can be very unforgiving if there's a mistake that's made

John Curry Nasa

"We have heard by the grapevine that they have made some progress with getting him signed. But we have not gotten that official yet," Dianne Murphy, a space station manager, said.

The Russian space agency has said Bass's late payments could lead to the mission being scrapped.

The singer is currently training in Star City, outside Moscow, to achieve his ambition to be the third space tourist.

Nasa is already planning for Bass and his cosmonaut crew to visit Johnson Space Center in Houston later this month for a full week of training.

Decision wait

Bass would be the first space tourist to use corporate sponsors and TV shows to help finance the trip.

"They expect all that to kind of come together here very shortly," Ms Murphy said.

Bass is also still waiting on a decision from a "crew operations panel" representing the US, European, Japanese, Canadian and Russian space agencies.

The group has been reviewing the matter since mid-July, when the Russians formally submitted Bass's name for the upcoming launch of a Soyuz spacecraft.

The Russians should have provided the names of the crew at least six months before the flight, to allow for adequate training and preparation.

Necessary training

But the list came three months late, mainly because of the delays in the contract negotiations with Bass.

Murphy said Bass could still fit in all the necessary training.

As far as teaching him space station safety, "we can do that within a couple of months," she said.

"Space flight can be very unforgiving if there's a mistake that's made," said flight director John Curry.

"Those are the kinds of things that we'll make sure that all three crew members are trained for, Lance being one of them if he ends up flying."

"It will be just like we've done with every other crew," Curry added.