Environmentalists are opposed to the expansion
A decision on the expansion of Heathrow airport has been delayed, the government has announced.
Transport Secretary Ruth Kelly had been expected to give a ruling in August about the plans for the west London airport, including a third runway.
But Ms Kelly said there was still work to be done in assessing the views of 70,000 individuals and organisations consulted on the expansion.
She added a decision would be made "before the end of the year".
In its 2003 aviation White Paper, the government said it supported Heathrow's development subject to strict air quality and noise level targets being met and as long as public transport access could be improved.
On Tuesday, Ms Kelly said her department officials were still analysing the responses to the consultation which was announced last November.
She added: "We also want to be sure, given the socio-demographic mix in the Heathrow area, that we fully understand how airport development might affect different groups in terms of race, disability, age or gender."
Operator BAA has said Heathrow is "jam-packed" and needs a third runway to remain competitive globally.
Environmentalists have always been strongly opposed to the idea, and the Conservative leader David Cameron recently questioned the need for a new runway.
Campaigners opposed to the planned expansion say it would have a serious impact on hundreds of thousands of homes in the area.