Isabel Dedring, vice chair of TfL and deputy mayor for transport, said they would be bidding later this year to take over the Anglia & Southeastern franchises.
Both franchises will be awarded by the Department for Transport and TfL is hoping to beat commercial train operators in order to bring the London Overground experience to the routes.
Set up in 2007 and controlled by TfL, London Overground frequently tops the UK’s rail performance league tables and offers integrated Oyster fares.
A major investment programme has seen the network benefit from new trains and refurbished stations and platforms.
Labour’s Val Shawcross, deputy chair of the Assembly’s transport committee, said TfL enjoyed “cross party support” for the bids.
