Transport Secretary Geoff Hoon said he recognised there were "strong views" on the issue and he intended to give it "proper consideration".
The BBC reports the cabinet is split over the third runway plan. More than 140 MPs – including 50 Labour MPs – have signed a Commons motion urging the government to consider the alternatives to a new runway.
In a statement, Mr Hoon said the government had made it clear it supported a third runway at Heathrow – subject to environmental controls. He said a consultation into the impact of such a project had finished on 9 November and he had begun to consider the evidence, including 70,000 responses. "I share the desire on all sides of the House, and among the wider public for this issue to be resolved. I am equally aware of the importance of reaching the right conclusion," he said.
"I know that there are strong views across a range of interests. I will ensure that I give proper consideration to the evidence before me and will therefore take more time before making an announcement to the House, in January 2009."
Speculation for reasons other than the "proper consideration" ranges from a split cabinet to fears over a commons defeat through a back-bench revolt, but backers of the scheme willbe worried about this loss of momentum.