A new spaceship could be ready to replace the nation's aging shuttle fleet by 2011 ¡ª three years ahead of schedule ¡ª if lawmakers added money to NASA's proposed budget, the head of the space agency told a congressional panel on Tuesday.

NASA Administrator Michael Griffin said that date is the earliest the new spaceship, or crew exploration vehicle, could be developed no matter how much money the agency received.

Currently, the target date for building a new vehicle is 2014.

With his pitch to Congress, Griffin underscored a point he has made previously about completing the spaceship on a faster time frame.

Pressed by Sen. Bill Nelson, D-Fla., Griffin acknowledged an additional $1 billion could accelerate the program's completion.

The shuttle is to be retired in 2010, and lawmakers are concerned about when a replacement will be ready.

"If money were not an issue ¡ª going back to Apollo kinds of days ¡ª then I think it would be no technical problem to have an operational system available in five to six years," Griffin said after testifying before a subcommittee that oversees NASA spending.

President Bush's budget calls for a 3.2 percent increase in NASA spending over last year. The House and Senate have authorized an additional $1.1 billion, but that is only a guide. The money must be appropriated by both chambers.

A Senate appropriations subcommittee was to scheduled to meet Wednesday to consider the proposed increase.

NASA will be shelving its three aging space shuttles in four years. The next generation of spaceships is supposed to carry astronauts to the moon by 2018 and eventually to Mars.

The so-called "flight gap" between the shuttles and their replacement could affect research and American space competitiveness, lawmakers said.

"We don't want a hiatus because we think that puts us in a security risk position," said Sen. Kay Bailey Hutchison, R-Texas.