Campaigners opposed to Heathrow's proposed third runway are hoping thousands of people will attend a rally against the airport's expansion on Saturday.

A coalition of local residents and environmentalists are to march from Hatton Cross underground station in west London to the village of Sipson, where some 700 houses will be razed if the expansion goes ahead.

"We're hoping for 10,000 people", Tamsin Omond, a member of the "Plane Stupid" group, told Reuters. The Metropolitan Police estimates 1,600 will attend the march.

In February, the "Plane Stupid" group scaled the roof of parliament to mark the end of public consultation on a third runway. It has threatened further direct action against government plans to expand Heathrow.

Prior to the start of the "Make a NOise Carnival", letters of support from Archbishop of Canterbury Rowan Williams and London Mayor Boris Johnson will be read out opposing the expansion.

Campaigners also plan to spell out a giant human "No" which they say will be visible from the air before MPs, local council leaders and environmentalists address the rally.

The government, business leaders and airport operator BAA say the world's busiest international airport must expand or lose out to continental rivals, damaging the country's economy.

But campaigners say expansion of aviation makes a mockery of government plans to cut carbon emissions.

"The size of the runway is like putting Gatwick next to Heathrow and would emit the same amount of annual carbon dioxide emissions that Kenya does," said Omond.

The public consultation over the expansion ended in February. The government is expected to make a final decision later this summer.