The commander of the international space station said today if the shuttle remains grounded for a prolonged period, and if the Russians cannot produce more Progress supply ships, the orbiting laboratory may not be able to support even two-person "caretaker" crews for any extended period.

It is a complex situation under daily, heated discussion by NASA, the Russians and their international partners as the agencies struggle to reconcile conflicting requirements in the wake of the Columbia disaster and the indefinite grounding of the shuttle fleet.

A European wire service reported today that Yuri Koptev, head of the Russian space agency, had appealed to the European Space Agency to help fund development of additional Progress supply ships in exchange for permanent slots aboard the space station for European astronauts.

"We have made a proposal to our European colleagues: we are looking to make it possible for their astronauts to participate in permanent missions aboard the ISS, on condition that they agree to take on a certain financial contribution," Koptev said in Moscow.

NASA is barred by law from directly funding such missions.

Asked if the U.S. manned space program might be facing a more serious crisis than many now suspect, station commander Kenneth Bowersox said today "I get the sense it's a very serious situation and that we will be more crystallized in our will as a country after we work through it, we'll know for sure what we want to do in space."

"I know that's the way it is for me as an individual, I mean you don't step on a rocket, don't take on a long space mission without knowing exactly why you're doing it," he told CBS News. "And we're doing it because we want to explore space, we want to lay the bricks on the road to leave our planet. And I think as we work through the process, our international team will know better why we're doing this mission."

On a more personal note, Bowersox also said he and his Expedition 6 crewmates - flight engineer Nikolai Budarin and science officer Donald Pettit - took advantage of regularly scheduled medical sessions with doctors on the ground to receive grief counseling after the Columbia disaster.

"As a matter of fact, there are planned sessions for us with our psychological support on the ground on a regular basis and we pretty much continued those," he said. "We received some good advice from them on how to deal with the situation. But for the most part, they prepared us before we ever launched for such an occurrence and I think our psychological team did a great job there."

Asked for an example of what the doctors provided in the wake of the Feb. 1 loss of Columbia, Bowersox said "for one thing, we've talked a little bit about standard grief responses and the type of emotions you might feel. We also talked a little bit about the best way to work through that grief response and we talked about one of the best ways to receive support on board is to try to support the folks on the ground right now."

Bowersox, Budarin and Pettit, launched Nov. 23 and working through their 89th day in space today, originally planned to return to Earth aboard the shuttle Atlantis in March. That mission was to have ferried up a fresh crew, but the shuttle program is now grounded. While no final decisions have been made, it is all but certain the Expedition 6 crew will land in May aboard the lab's Russian Soyuz lifeboat.

The Soyuz lifeboats must be replaced every six months and the next craft is scheduled for launch April 26. That so-called "taxi" flight originally included commander Gennady Padalka and European Space Agency astronaut Pedro Duque. After a weeklong stay aboard the station, Padalka and Duque had planned to return to Earth aboard the older Soyuz, leaving the fresh lifeboat behind at the station.

All of those plans are now up in the air. NASA, the Russians and their international partners are in intense discussions about launching a so-called "caretaker" crew to replace Bowersox and company. The caretaker crew - made up of just two crew members because of the station's limited on-board water supplies - would remain in orbit until at least October when another fresh Soyuz is scheduled for delivery.

One member of any caretaker crew must be a Russian Soyuz commander. NASA says the other member of the crew must be an American with the comprehensive training necessary to maintain systems in the station's U.S. modules. Several names have been bandied about in recent days, but no final decisions have been made.

This is a complex issue for the station's international partners. The Russians were counting on income from launching two European Space Agency astronauts this year on Soyuz taxi flights. If Duque is bumped from the April mission, which appears all but certain at this point, it's not clear how the Russians would make up for the funding shortfall.

This is potentially significant down the road because NASA is barred by law from buying Soyuz or unmanned Progress supply flights directly from the Russians. If the shuttle fleet remains grounded for more than a year, the Russians would have to increase the Progress flight rate to deliver the supplies and fuel necessary to periodically boost the station's altitude and to keep even a two-man crew in orbit.

"If we were to keep the same number of Progresses we have per year in the current plan, it would be difficult to maintain the station as we currently are running it," Bowersox said today.

"We'd probably have to back off a lot from what we're doing, maybe even go to less than two people on board. But if we increase the number of Progresses, we should be able to maintain operations, at least from all the data we've seen from the ground. And of course, that's still being studied."

The next unmanned Progress launch is targeted for June 8. Another follows on Sept. 18 and the one after that on Jan. 30. If that schedule holds up, it's not clear whether enough supplies will be available - in the continuing absence of the space shuttle - to keep the station manned a full year.

"We must be ready for the worst-case scenario," Koptev said in the AFP wire story. "If we don't take the decision today on the construction of the necessary number of vessels and don't ensure the financing, there will be no vessels in 2004 as currently scheduled. Next year risks being critical in terms of serving the station with fuel and water."

For their part, Bowersox, Budarin and Pettit say they would happily remain in orbit a year or more if necessary.

"We came up here thinking we might be the shortest mission ever," he said today. "We were happy to get to come to the station at all, but we were hoping we would get to stay a little bit longer. We were mentally prepared for a year because you don't want to be disappointed thinking you're going to come home in six months and then not get to do it.

"So mentally, you just have to be ready for up to a year and we weren't joking about that, we really are," he said. "Nikolai's been on a space station for seven months before and he says he's definitely ready to stay at least that long and knows that it's not a problem. So we would be happy to stay longer aboard space station, that would be a good thing for our crew."

As for landing in a Soyuz whenever they do come home, Bowersox said his crew will be properly trained and ready.

"We went through the full course of training that's required for entry on the Soyuz, our friends in Star City insisted on that so that if we would need to use it, we'd be safe and we completed that course successfully," he said.

"The second thing is we do have trainers and information handbooks up here that we can study to help us prepare. Of course, the best training device we have is the Soyuz itself, we can go in there and work with the switches and panels and prepare ourselves for entry. But if it is decided we'll come down in the Soyuz, we'll have dedicated training sessions with specialists on the ground to make sure our skills are peaked up a little bit better than they are now before we come home."