Countdown clocks began ticking again Tuesday for the delayed shuttle Atlantis and officials said it was on track for a second launch try Thursday, weather permitting, to carry a Venus probe into space.

"The bird looks real good," said NASA test director Ronald Phelps. "I think we're all confident right now we can meet the launch on schedule, pending no weather impacts or anything like that."Atlantis's abbreviated countdown began on time at 8 a.m. Tuesday for a launch at 1:48 p.m. Thursday, six days after a short circuit in a fuel pump last Friday grounded the shuttle just 31 seconds before liftoff.

Air Force Capt. Thomas Strange said the forecast for launch time Thursday was generally favorable, with a 70 percent chance of acceptable conditions, but he said high winds could be a factor.

Atlantis's crew - commander David Walker, 44, co-pilot Ronald Grabe, 43, Mary Cleave, 42, Mark Lee, 36, and Norman Thagard, 45 - was scheduled to fly from Houston to the Kennedy Space Center late Tuesday for final preparations.

Engineers at the spaceport worked around the clock over the weekend and into Monday to replace a faulty hydrogen fuel recirculation pump in Atlantis's engine room, along with a 5-foot hydrogen fuel line that appeared to be damaged after the pump shut down.

The repair work went faster than expected and NASA managers Monday "decided to proceed toward a possible launch of (Atlantis) no earlier than Thursday," the agency said in a statement.