CAPE CANAVERAL, Fla. (MARCIA DUNN, AP Aerospace Writer) — Spacewalk or space delivery?

That's the question facing NASA as space station flight controllers try to revive a crippled cooling loop.

Half of the International Space Station's cooling system shut down Wednesday because of a bad valve. NASA is attempting to regulate the temperature of the disabled cooling line, with some success. The faulty valve had made that line too cold.

The two Americans on board may need to make spacewalking repairs, beginning Thursday. That's the same day an unmanned rocket is supposed to hoist a space station cargo ship from Virginia. NASA said Monday that it expects to decide Tuesday which should take priority — repairs or restocking.

Orbital Sciences Corp.'s Cygnus cargo ship has already been delayed a couple days because of the cooling problem in orbit.