Prequalification is expected by the end of April, with some companies claiming that rival consortiums do not have the necessary resources for a sustained bid.

'There are only six companies worldwide who do high-speed technology, so some of these bids do not have the key ingredients,' says an official at a Saudi partner to one of the consortia.

'We are expecting at least two from the seven will be disqualified at prequalification.'

A French consortium includes Alstom, maker of the TGV high-speed trains. The French rail authority SNCF, which as an adviser to the Saudi Rail Organisation is barred from bidding directly, is expected to be involved through one of its subsidiaries.

A German consortium of Siemens and Deutsche Bank is partnered with Saudi Binladin Group.

The Italian aerospace and defence group Finmeccanica is partnered with Saudi Oger and the Italian state rail operator Gruppo Ferrovie Dello Stato, while a Spanish bid will come from Talgo and the country's national rail authority Renfe.

Further tenders are believed to have come from both Japan and Russia.

The Saudi Rail Organisation added that companies from Australia, China and the UK were also involved in the bidding.

Qualified consortiums will be asked to submit requests for proposals by the end of 2007.