An aviation group is trying to strike a deal with environmentalists over airport expansion in the South East.
An airport at Cliffe is one option the government has suggested
Freedom to Fly, which represents companies such as BAA and Virgin Airways, says it will drop support for plans for an airport at Cliffe on the Hoo Peninsula.
In return it wants green campaigners such as Friends of the Earth to drop their opposition to the expansion of airports such as Heathrow and Gatwick.
Building an airport at Cliffe and expanding other airports are options in a government consultation about the future of aviation and airport services over the next 30 years.
We would back legitimate legal action to protect people's health and to protect their interests
Paul de Zylva, Friends of the Earth
Freedom to Fly says the agreement would speed up the consultation process.
A letter has already been drafted to Transport Minister Alistair Darling which aviation companies say they will dispatch once they have received assurance from green groups that they will not mount a legal challenge against excluding Cliffe.
Dan Hodges, from Freedom to Fly, said: "We are prepared to write to Alistair Darling asking him to withdraw consideration from the Cliffe option providing we get a clear commitment from the environmental groups, in particular AviationWatch and Friends of the Earth, that they will withdraw their own threat of legal action."
But Paul de Zylva from Friends of the Earth said it was not an acceptable offer.
He said: "We would back legitimate legal action to protect people's health and to protect their interests.
"If airport expansion was approved that would lead to a breach of air quality and other such concerns that is legitimate legal action.
"That is nothing to do with extending the consultation."