Space shuttle Atlantis is set to blast off on its final flight next week, heading to the International Space Station, carrying up a crew of six and a load of supplies.

Nasa's top managers agreed to set today week as the launch date. Liftoff would be at 2.20 p.m. Much of the payload is crammed inside a Russian-built module that will be attached permanently to the orbiting lab complex. The astronauts will venture out on three spacewalks to plug in fresh batteries and tack on a spare antenna.

The 12-day mission is scheduled to be the last for Atlantis. Nasa is retiring its three shuttles at the end of this year. After this flight, only two will be left.

But Atlantis won't be dismantled and head to a museum when the flight is over. Instead, the spaceship will be prepped for a potential rescue mission for Nasa's very last shuttle flight. That final trip, by Endeavour, is scheduled for November at the earliest.

Discovery is supposed to make its last trip in September.

At a news conference, Nasa's shuttle programme manager noted that the mission comes on the heels of Discovery's recently completed trip to the space station.

"It's 15 days since we last landed. Nine days until we launch," programme manager John Shannon said. "This is the kind of pace that this team thrives on."

Launch director Mike Leinbach said shuttle workers are not distracted by the end of the programme - at least not while they're on the job. Any venting is saved for lunch time or the end of the day, he said.

"They know the end is coming and they're making their plans," Mr Leinbach said.

"We've gotten past the denial stage of change, and we're into the exploration and the acceptance change."

President Barack Obama visited Kennedy Space Centre on April 15, laying out a strategy for sending astronauts to an asteroid by 2025 and Mars by 2035.

In doing so, he cancelled plans made by his predecessor in 2004 to return astronauts to the moon. He also did not call for any additional shuttle missions, as some had hoped.

If there is to be one additional flight to the space station, Nasa officials said they would like to know by June so they have enough time to train a crew and prepare the cargo.