But Stephen Joseph, deputy-chief executive of the body co-ordinating the regeneration of the Thames Gateway, made it clear that this might not be sufficient to kick-start the redevelopment of the area.
Joseph, number two at the Thames Gateway London Partnership, said that without funding guarantees for links to central London, developers would not be willing to invest in the Thames Gateway.
The development of the Thames Gateway, the largest brownfield site in Europe, has long been a strategic aim of governments. It is the key to deputy prime minister John Prescott's plans to remedy the housing shortage in Greater London, but only if private investors can be found.
A source close to CrossRail said: "The company is looking to give the government a range of choices, not just one all-or-nothing option, in case extending the line to Ebbsfleet fails Treasury cost-benefit tests.
"To be responsible, it will come up with a plan B so that the entire scheme is not held to ransom."
CrossRail had initially hoped to be given enough money to fund the line through Canary Wharf and beyond to Ebbsfleet in Kent. It is now believed to be willing to offer the government a fallback option, going only as far as Dartford or Plumstead.
The Thames Gateway London Partnership has long feared that Cross London Rail Links would ask the government to fund a shorter route. It believes there is no guarantee that any extension of the scheme would secure government funding.
A CrossRail spokesperson said: "We are currently evaluating the options for engineering, operational and financial reasons. Whichever route we come up with will be extendable or enlargeable."