Ron Marsh, head of business development at the consulting engineer, said the consortium members would put their signatures to a pre- qualifying bid at a meeting scheduled for this afternoon.
He said that the bid would go ahead regardless of the fine detail of the route, which John MacGregor, the Secretary of State for Transport, will announce next week.
The final route is expected to broadly follow the eastern approach proposed by Ove Arup and accepted by the Government in 1991. Once announced the line will be safeguarded and cannot be altered.
The approach, through the East Thames corridor and terminating at Kings Cross or St Pancras, was preferred to four routes through south-east London originally proposed by British Rail.
Next week's announcement is expected to confirm St Pancras as the preferred terminus, with an extra two miles of tunnelling to counter protests from Islington residents. Forty per cent of the people affected by the route live in the north London borough.
The commitment to bid follows the Government's decision earlier this week to increase the level of public sector funding for the pounds 3bn railway line, the first main line to be built this century.
The Treasury has agreed to provide up to half the cost of the scheme, about pounds 1.5bn. Ministers have also agreed that revenues from international passenger services from Waterloo will be made available to the builders of the link.
This will provide a source of income during the early years of the project and help to prevent the funding crisis that plagued the building of the Channel tunnel.
The Channel Tunnel Act specifically prevented the Government giving British Rail money to improve international rail links, but the decision to use the link for domestic commuter services as well enabled it to make a contribution.
Ove Arup's announcement will also give a significant boost to a campaign backed by Newham Council and the London Docklands Development Corporation for Stratford to be chosen as one of the intermediate stations on the line.
Ove Arup held a meeting earlier this week with the Stratford Promoter Group, a consortium headed by Tarmac and P&O, which has been lobbying for a second London station on the link. It is known to favour Stratford and will include it as an integral part of its bid.
The Stratford group argues that a station with good links to the capital's public transport network is essential if the link's final terminus is not to become overburdened with passengers using the route as both an international terminal and a commuter line.
Stratford is the only proposed station to contribute to the regeneration of east London but it is thought to have received a lukewarm reaction from Union Railways, the BR subsidiary that will become the vehicle for the development of the line.
Other possible stations include Ebbsfleet, between Gravesend and Dartford, an option backed by the local authorities and Blue Circle. A third possibility is Rainham, which has the support of the borough of Havering and Amec, the construction company.
After bids have been invited, a bill for the construction of the 68- mile link will be introduced, probably in the autumn. Construction is expected to begin in 1997, with completion about five years later.
Ove Arup expects to be in competition with three or four other consortia but said it would be surprised if more than half a dozen groups came forward.
Eurorail, a venture between Trafalgar House, BICC and GEC, is widely expected to bid. It was the preferred partner on the routes suggested by British Rail through south-east London but withdrew after the routes were rejected.
Other likely bidders include Hochtief, the German construction company, and a grouping of Continental players being put together by Swiss Bank Corporation.Reuse content