Brief The threat of lightning has forced NASA to postpone the launch of the Dawn mission to the asteroid belt by 24 hours.

The warning came as engineers were preparing to fuel the Delta II rocket that will carry the probe into orbit and beyond.

The temperature of the rocket's second stage had also risen too high to allow fuelling to begin, so engineers are now pumping cool air into the aerodynamic cover, or fairing, to get the temperature back down to 58 of those American degrees Fahrenheit. That is 14.5°C in real money.

The mission is due to launch on Sunday 8 July atop a Delta II rocket, and the countdown dress rehearsal is due to start today, Friday.

But the prospects are not great for Sunday's launch: weather forecasters say there is a 60 per cent chance that conditions will not meet those required by the space agency's stringent safety guidelines. ®

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