SpaceX CEO Musk after unveiling the Dragon V2 spacecraft. Thomson Reuters SpaceX will wait another 24 hours before it launches its Falcon 9 rocket out of its Cape Canaveral launch site.

SpaceX CEO Elon Musk tweeted four hours before it was supposed to launch that the crew was punting for another 24 hours.

Launching on Monday night gives the rocket a 10% better chance of a good landing, Musk said. The additional time also gives the liquid oxygen further time to chill, said Orbcomm, one of the companies also involved in the launch.

Monday's launch will be the first time that SpaceX will have attempted a rocket touchdown on land, so the company clearly wants to go with the time window that gives it the best shot at achieving that goal.

The launch time is now set for Monday, December 21, at 8:34 p.m. ET in Cape Canaveral, Florida.