Speaking on Capitol Hill, NASA Administrator Sean O'Keefe said today the space station's international partners have agreed to keep the lab complex manned with rotating two-person crews launched aboard Russian Soyuz ferry craft until space shuttles return to flight.

The first such crew, taking a fresh Soyuz lifeboat to the station, is scheduled to take off in late April or early May. The station's current crew - Expedition 6 commander Kenneth Bowersox, flight engineer Nikolai Budarin and science officer Donald Pettit - will return to Earth four to six days later aboard the lab's current Soyuz lifeboat.

The launch date is somewhat uncertain due to ongoing discussions of lighting requirements for landing of the ISS-6 crew.

In any case, the Soyuz lifeboats must be replaced every six months and the station partners now plan to use those so-called taxi flights to rotate two-man crews as well.

"As of yesterday, we were able to reach a very specific set of solutions on that approach," O'Keefe told the House Science Committee today. "The deliberations have been very constructive and all the partners are acting like partners in the development of a partnership solution."

He said the partners "agreed to use the Russian Soyuz emergency egress spacecraft that are rotated twice a year to international space station to rotate the crews, the expedition crews, aboard the station for this interim period."

O'Keefe said the new Expedition 7 crew will be made up of a Russian Soyuz commander and a NASA astronaut trained to operate U.S. systems. Both are already in training at Star City in Russia, but O'Keefe did not identify them. NASA officials later said four men - cosmonauts Yuri Malenchenko and Alexander Kaleri, along with NASA astronauts Edward Lu and Michael Foale, are in training and that two of them, one Russian and one American, will be named next month to serve as the ISS-7 crew.

U.S. and Russian sources have said that Malenchenko and Lu will make up the ISS-7 crew while Kaleri and Foale will replace them in the fall as the ISS-8 crew. NASA officials would not confirm that breakdown, however.

Malenchenko, Lu and Kaleri already were in training to replace Bowersox and company in March. The ISS-7 crew planned to ride the shuttle Atlantis into orbit, but loss of the shuttle Columbia Feb. 1 grounded the shuttle fleet and prompted a reassessment of how to operate the station in the meantime.

Instead, the revised ISS-7 crew will ride a Soyuz to the station and dock at an Earth-facing port on the Zarya module. The current Soyuz, the one the ISS-6 crew will come home in, is docked to the Pirs airlock module.

The primary source of fresh water for station crews is the shuttle, which produces water as a byproduct of generating electricity in its hydrogen-oxygen fuel cells. Without regular shuttle visits, the station cannot support a three-person long-duration crew, forcing the partners to explore options for two-person caretaker crews.

The plan at present, O'Keefe said today, is to launch fresh two-person crews to the station every six months until the shuttle can resume flights. The ISS-8 crew will ride another Soyuz to the station in October if the shuttle fleet is still grounded at that point.

At the same time, he said, the international partners have agreed to accelerate the production of unmanned Progress spacecraft to deliver the supplies necessary to keep even two-person crews in space. Without additional Progress capsules, the station cannot remain manned much past the end of the year.

"So the partnership has agreed to that," O'Keefe said. "We are all in agreement on the approach on how we will proceed in order to maintain that capacity and to assure that we can operationally continue this important laboratory condition."

But he provided no details about how the Russians would finance the accelerated development of Progress supply ships or how they would be compensated for losing income from the European Space Agency. ESA astronauts had been scheduled to visit the station twice, in May and October, as members of Soyuz rotation flights. Russia charges between $20 million and $30 million for such flights and in the short term, at least one of the ESA flights will have to be deferred, depriving the Russian space program of much-needed cash.

An ESA astronaut is expected to be aboard in October when the next Soyuz is launched, but he will return to Earth with the two-man ISS-7 crew.

Under the Iran Non-Proliferation Act of 2000, NASA is barred from directly financing Russian launchings or helping pay for development of additional Progress supply ships. Russian space officials already have approached their ESA counterparts to discuss the option of European financial support of Progress development in exchange for seats on future long-duration crews.

Nick Lampson (D-Texas) said today he planned to introduce legislation to amend the Iran Non-Proliferation Act to permit possible U.S. financial assistance.

"I believe we need to ensure the space station remains operational while the shuttle fleet is grounded," he said. "Therefore, I plan to introduce legislation today that amends the Iran Non-Proliferation Act of 2000 to allow NASA to purchase additional Soyuz and Progress vehicles if the president notifies Congress they are needed to ensure the safety of the crew aboard the international space station and to maintain its operational viability while the space shuttle fleet is grounded."

In response to a question from Science Committee Chairman Sherwood Boehlert (R-N.Y.), O'Keefe said the partners would not hesitate to bring a crew home and to leave the lab complex unmanned if safety is ever compromised.

"What is it that would motivate us to decrew or abandon the space station? Any safety consideration would immediately motivate us to direct the crew to get into the Soyuz vehicle and return home and dim the lights," he said.

"Because we do not want to compromise the safety of those human beings one moment. Our attempt here is to assure we can continue to support their activity, to maintain some science and research objectives aboard, not nearly as optimum as we can now, but to maintain this so we can get to the point of returning to shuttle flight."

Answering another question, he said the station could be safely operated in an unmanned mode for just six months to a year, and that assumes no major problems crop up that would require astronaut repair work.

"Assuming all that stayed exactly right and we could move the orbit of the international space station to avoid debris, to keep its altitude at the appropriate orbit levels, we could probably do that for six months to a year, assuming no other unforeseen circumstances," he said.

Any major problems, in the absence of a crew, "could compromise its continued operations."