The Tories have called for a rail-link instead of an extra runway
The British Airports Authority (BAA) is calling for a high-speed rail link to Heathrow to complement a third runway at the west London airport.
The company believes Heathrow needs both if it is to compete with other European airports.
The airport operator will make the call to politicians and rail organisations at a rail conference in London.
A decision on the third runway at Heathrow will be made by the government by the end of the year.
BAA will point out that in Paris and Frankfurt, airport capacity is built to complement high-speed rail travel.
The company believes these airports represent a threat to Heathrow's competitive position, which in turn will affect the UK's ability to compete.
BAA director of planning and surface access Stuart Condie will tell the conference that a three-runway Heathrow would strengthen the UK's connections with global markets, including China and India.
And a high-speed rail link would spread the economic benefits across the UK, he will argue.
Transport unions and recently the Conservative Party have called for high-speed rail connections to be built instead of a third runway.
The Tories are proposing to create a new line linking London St Pancras, Birmingham, Manchester and Leeds - saying it would cut Heathrow flights by 66,000 a year.
But Mr Condie will tell the conference: "Choosing rail capacity over airport expansion, or air over rail for that matter, is a false and dangerous choice that will leave the UK at a competitive disadvantage at precisely the wrong time."