The bus firms are competing to run the tram system
Nottingham's two biggest bus companies are competing to build the city's tram extension.
Bidders for the £400m project were revealed by the city council on Wednesday morning.
One of the two consortia bidding for the contract includes Nottingham City Transport, the city's main bus service provider, and train-maker Bombardier.
The other contending consortium involves bus operator Trent Barton. The result will be revealed in 2011.
The winning consortium will run the existing route and build and operate new lines out to Chilwell and Clifton.
Completed tenders are expected to be received by May 2010.
Chris Deas, tram project director at the council, said: "We are very pleased that the project has attracted the interest of two consortia of such calibre, especially in the current economic climate.
"Each includes organisations that can bring valuable skills and experience to Nottingham.
"The involvement of Nottingham City Transport and Trent Barton will ensure both consortia have a full understanding of the local public transport market."
It is expected that Nottingham City Council will award the winning bidder with the contract in August 2011.
Construction of NET Phase Two is due to start in the autumn of that year. The two new lines should be operational by late 2014.
Nottingham's two biggest bus companies bid for a contract to build the city's tram extension.