The extension will replace the existing overland link between Canning Town and Stratford. Work will include track and signal replacement to accommodate the DLR route, upgrading Canning Town and West Ham stations and fit-out works at Stratford International.
Three new DLR stations - Star Lane, Stratford High Street and Abbey Road - will also be built under the deal.
Work is set to start in May 2007 with completion due for February 2010.
Transport for London approved plans for DLR to aptly for a Transport and Works Act order for the scheme in May 2005.
Firms have until the end of July to express an interest.