The 68-mile (109km) London to Folkestone high speed rail link has been put up for sale by the government.
The route, which runs from London St Pancras to Folkestone, has stations at Stratford, east London, and Ebbsfleet and Ashford in Kent.
Eurostar trains to Paris and Brussels and Southeastern's Japanese-built Javelin trains operate on the track.
The sale, likely to bring in around £1.5bn, could open it up to more operators, possibly from overseas.
The route, known as HS1, cost £5bn to build and is currently run by London and Continental Railways under the control of the Department for Transport.
Moves to offer the rights to operate the route were first announced by the Labour government last year.
The successful bidder will become the owner of HS1 Ltd, with a 30-year concession to run the line and stations.
Launching the sale at St Pancras, Transport Secretary Philip Hammond said: "HS1 is a national success story and a world-class railway operating to international standards.
"The money generated by this sale will make an early significant contribution to the crucial task of reducing the public sector debt."
He said the sale to private bidders could open up the route to more operators.
"This is part of the government's approach to making our national assets - and every taxpayer pound - work harder.
"The government does not have to run everything directly - we need to take prompt action where private enterprise can provide both a better deal and a superior service to the public."
Mr Hammond said he expected the government to be able to announce the winning bidder before the end of the year.
Following the sale, the performance of HS1 Ltd will be independently regulated by the Office of Rail Regulation to safeguard passengers' interests.
The Transport Secretary restated the government's aim to link HS1 to HS2, the north-south high-speed line the government hopes to start in 2015.