"We are ready to go," Michael Griffin, administrator of the National Aeronautics and Space Administration (NASA), told a Congress committee.

NASA experts will hold a final "flight readiness review" meeting on Wednesday and Thursday. And the US space agency will then set a launch date for Discovery, with a blastoff window between July 13 and July 31.

Griffin's optimism contrasted with a panel set up to oversee NASA's resumption of shuttle flights.

The Return to Flight task force said in a report Monday that the space agency had been unable to eliminate the possibility of pieces of foam and ice breaking off the external fuel tank and striking the shuttle at lift-off -- the cause of the Columbia disaster.

The committee, which includes two former astronauts, said NASA had failed to "totally meet" three of the 15 conditions set for the resumption of flights.

But several members of the panel said NASA should still be allowed to resume the flights as it had clearly boosted safety after Columbia.

"We feel that it is a safe vehicle to fly," said panel member Joseph Cuzzupoli.

Griffin told the House of Representatives' Science Committee: "I have been participating in every technical review.

"I have required a picture where we are. I have been tremendously impressed by the team's work, and I think based on what I know now, we are ready to go."

Engineers finished last week a detailed examination of modifications carried out to the space shuttles since Columbia caught fire and broke apart as it re-entered the Earth's atmosphere on February 1, 2003, killing all seven crew members.

The disaster has been attributed to damage sustained by the spacecraft after it was hit by chunks of insulating foam that broke off during liftoff.

All US space shuttles have been grounded since and NASA has been forced to reform its administration and carry out major changes to the shuttle programme.

Discovery has a new external fuel tank, while a new heater has been added to the fuel feedline pipe. The heater is designed to minimize potential ice and frost buildup on a part of the pipeline that carries liquid oxygen to the main engines.

The new tank has also been fitted with temperature sensors and accelerometers to gather information about the tank's performance and measure vibration during flight.

Shuttle programme director Bill Parsons said Friday "There is no big technical issue we are working on currently." He added: "We feel the risk is acceptable."

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