Top NASA (search) officials debated Thursday whether to postpone a May liftoff for the first space shuttle flight since the Columbia disaster, based on the latest launch-debris analyses and the possible need for extra repairs.

NASA spokesman Allard Beutel said the space agency would have no comment on the outcome of the meeting until Friday, although there were signs that the launch had been put off. NASA and contractor managers canceled reservations at hotels near Cape Canaveral (search) and rebooked for mid-July.

Preparations for the May 22 launch for a 12-day mission had been put on hold for at least a day because of the deliberations. Beutel said shuttle managers wanted to decide whether they can accomplish everything they need to do in time for a liftoff then.

If the Shuttle Discovery (search) is not flying by early June, it will have to remain grounded until mid-July because of NASA's desire for a daylight launch.

Senior NASA officials convened late in the afternoon and their session lasted hours, until evening. Beutel said the space agency would have no comment on the outcome of the meeting until Friday.

Earlier Thursday, Beutel said the meeting was "to see exactly where we are and what additional work may or may not lie ahead of us to get back to flying safely."

NASA officials and engineers spent two full days this week conducting an extra review of the dangers of debris falling off the shuttle's external fuel tank during liftoff.

Specifically, the space agency more closely analyzed the possibility of ice forming at two particular spots on the tank once it is filled with super-cold fuel, and the chances of foam insulation breaking off from a spot at the top of the tank.

The main lingering concern is potential ice buildup on the expansion joints of a 17-inch-diameter liquid oxygen feedline that runs 70 feet down the lower half of the 154-foot tank. The joints have produced ice in the past, and after the Columbia accident, NASA devised a foam skirt, or so-called drip lip, to wick moisture away from the joints.

Engineers believe this will reduce ice formation at that spot by 50 percent, but shuttle managers may opt for a more comprehensive, time-consuming repair, like installing a heater. To add a heater, the shuttle likely would have to be removed from the launch pad and hauled back to the Vehicle Assembly Building, which would add days if not weeks to launch preparations.

Columbia was brought down in February 2003 by a gash in the left wing that was caused by a suitcase-size piece of foam that broke off the tank during liftoff. All seven astronauts were killed 16 days later during re-entry.

The space agency wants the first two post-Columbia launches held in daylight to ensure good photography of the shuttle and its fuel tank, which has been modified to prevent big pieces of foam insulation from coming off. That is why Discovery must fly by early June, or else wait until mid-July.