MANASSAS, Va. — Leadership of the United States in space travel and exploration is slipping away, NASA Administrator Michael Griffin said.

While the United States became the first nation to reach the moon with a manned mission and achieved stupendous strides in technology development, that lead has been obliterated, Griffin said.

“We had a lead of four decades,” Griffin recalled. “We do not have that lead any more.”

He said it is up to the United States to decide whether to retain its stellar role as the preeminent nation in mastering the world of flight and space travel.

At this point, China is performing as many manned flights as the United States, and Russia sends far more manned missions aloft, Griffin said.

He spoke at a dedication of a new Aurora Flight Sciences product development facility, The company produces unmanned aerial vehicles that can aid Earth-bound U.S. military forces, and also plans to produce the first aircraft to fly in the atmosphere of Mars, the ARES Mars Airplane.

Now comes a time of testing, he said, to see whether the United States has the will to retain its traditional lead in space, or whether it will be overtaken by competitor nations, to see “whether we will be preeminent in space, or one of many” nations competing there.

Griffin argued that the United States should settle for nothing less than to remain preeminent in the nether region.

He noted that millennia ago, the Romans created a vast empire in which they became the master of exploring and controlling the land. More than a millennia later, the British became masters of the sea, in a far-flung realm where the sun never set on the British empire.

Then, a century ago, the United States became the leader in mastering the art of flight.

“The choice is ours,” Griffin said. “Do we choose to master the defining art of our day? Or do we stand aside and let someone else” master the vast reaches above the planet?

As he spoke, he shared the stage with Rep. Frank R. Wolf (R-Va.), chairman of the House Appropriations Committee science subcommittee, which has jurisdiction over funding space programs. Also on the stage was Sen. John Warner (R-Va.), chairman of the Senate Armed Services Committee.

To be sure, Griffin acknowledged that space flight isn’t cheap, or easy.

“Space flight is expensive,” Griffin said. “It is difficult. It is dangerous.”

At this point, however, the current U.S. space program involves no ground-breaking accomplishments.

He spoke less than a month after the Space Shuttle Discovery scored a picture-perfect July 4 launch on a mission to the International Space Station (ISS).

It was only the second shuttle flight since the Space Shuttle Columbia disaster, in which a piece of foam insulation broke off the Columbia external fuel tank, hit the leading edge of the orbiter wing and punched a hole there. Later, during reentry, blistering hot gases of reentry rushed into the wing, causing structural failure that destroyed the orbiter. The crew was lost Feb. 1, 2003.

While changes to Discovery to lessen loss of foam insulation during a launch appear to have worked well, Griffin stepped back and said both the shuttle and the ISS provide mankind no more than low Earth orbit, a mere stepping-stone into space travel.

“Flying the space shuttle and the space station” doesn’t move dwellers of this planet into new realms, he said.

For the United States to retain its lead in space, it must “go beyond low Earth orbit,” Griffin said.

He didn’t trivialize the task of attaining that orbital place in space, but said it must serve a purpose toward greater missions. “Earth orbit is a step along the road, but the road has to lead somewhere,” he said: outward, to other heavenly bodies.

President Bush projected a vision of returning astronauts to the moon, and then sending manned missions to Mars and beyond.

But critics have said there is no corresponding commitment to provide new funding to finance these outward odysseys, which would cost billions of dollars.

Rather, NASA is proposing to take money, some $3 billion over five years, from its science programs to finance the exploratory programs, including the hardware to venture forth in the solar system.

Griffin later was asked whether this difficult choice shows that NASA requires an increase in its total budget funding.

But he demurred, saying, “I have to advocate the president’s budget” proposal to Congress.

One cannot have everything one might wish, simultaneously, he said.

“Some things are going to have to wait a bit,” he said. “We can’t do it all at once.”

However, what if Congress provides extra money, beyond the request? he was asked.

In that case, Griffin observed, “Congress has primacy” under the Constitution in writing and passing funding bills.