Similarly, the European Space Agency (ESA) has pledged in public comments support for keeping the space station permanently manned, even if that should mean temporarily giving up seats on Soyuz taxi missions in favor of flying the long-duration expedition crews.

NASA has not yet received any official word confirming those sentiments, but is aware of the widely reported comments coming from the international partners.

"Those are discussions that will be coming in the days and weeks ahead. We'll be meeting with our international partners soon and will start looking at our options," said NASA spokeswoman Debbie Rahn.

Many of the international partner's top officials will be on hand for Thursday's planned memorial service at the National Cathedral in Washington, D.C., and NASA managers plan to take advantage of that opportunity to brief them on the status of the Columbia investigation, Rahn said.

The next Soyuz taxi flight is currently scheduled for launch April 26 and is to include veteran ESA astronaut Pedro Duque. Another ESA astronaut, Andre Kuipers, is set to fly aboard aboard the October Soyuz taxi mission. Both astronauts will continue training for now.

A three-seat Soyuz spacecraft remains docked to the space station at all times to serve as an escape craft in case of an emergency. The Russian-built ship is certified to remain in space for only six months, so twice a year a fresh lifeboat must be launched.

On such taxi missions the new Soyuz is launched and docks with the station. The taxi crew then returns to Earth a week later, coming home in the old Soyuz.

Because it takes only two people to fly a Soyuz, the third seat is available for the Russian Space Agency to use as they see fit, which on two occasions so far has meant flying fare-paying space tourists.

American businessman Dennis Tito was the first in 2001, followed a year later by South African entrepreneur Mark Shuttleworth.

The president of one of the U.S. space tourist companies that played an important role in Shuttleworth's flight, Space Adventures, Inc., released a statement Wednesday supporting the decision to suspend space tourism flights if that will help NASA.

"Space tourism will advance as appropriate and we will continue to do what we have always done, to provide opportunities for the private explorer to experience the excitement and wonder of space," said Eric Anderson, Space Adventures CEO.

Although no decisions have been made yet, it is technically possible that the current Expedition Six crew of Ken Bowersox, Don Pettit and Nikolai Budarin could come home on the Soyuz now docked to the station after the new Soyuz is launched in April.

If that were the case, the new Soyuz flight likely would carry the Expedition Seven crew of Sergei Moschenko, Yuri Malenchenko and Ed Lu. The three are currently in Houston training for their ride into space aboard shuttle Atlantis.

Russian space officials say they are preparing for that possible eventuality.

"We will most probably take charge of manned flights until shuttle flights are resumed. Of course, the program of manned flights will have to be adjusted," said Yuri Semyonov, president of Russia's Energia Space Corporation.

But that doesn't necessarily mean Russia will begin building and launching additional spacecraft to the ISS.

"The space industry displays a lot of inertia. Even if the U.S. finances the construction of a Soyuz spacecraft now, it will be ready only in 2005. And by that time, the United States will have discovered the cause of the accident and shuttle launches will probably have been resumed," Russian space agency spokesman Vitly Sambros said Wednesday, according to Interfax.

Another Russian official, Vladimir Solovyov, has told media in Russia that the Expedition Six crew will come back after the next Soyuz is launched in late April or early May, according to Interfax.

Again, NASA officials say no decision has been made yet as those discussions haven't even started.

In the meantime, Ilya Klebanov, Russia's Industry, Science and Technology Minister, said Wednesday that his nation is prepared to help the United States continue work on the ISS and other international programs in the wake of the Columbia accident.

"Russia is shocked by this tragedy," Klebanov said, according to Interfax. "While the U.S. decides on its carrier vehicles, we are prepared to increase the work of our carrier vehicles."

A Progress freighter docked Tuesday to the ISS, delivering a ton of food, fuel and other supplies to the frontier outpost -- enough stuff to allow the Expedition Six crew to remain safely in orbit through at least June.

They were scheduled to begin unpacking the cargo ship on Wednesday.