Crossrail 2 chiefs are set for fresh talks with the transport secretary next month to secure backing for their funding proposals for the £31bn railway line.
The rail project that would serve stations throughout the south east was namechecked by the government during last week's Budget, but chancellor Philip Hammond stopped short of giving a concrete commitment to funding.
"We continue to work with TfL on the funding and financing of Crossrail 2," Hammond said on Wednesday.
Now transport bosses are due to meet Chris Grayling next month for feedback on revised funding plans, after the transport secretary said in July that London would need to meet half the costs of the project during construction.
Grayling has said he is a supporter of the project, but "given its price tag, we have to ensure that we get this right".
Earlier this month, London mayor Sadiq Khan criticised the request of meeting half the costs during the cost of construction, rather than afterwards, calling it an "onerous" challenge. Khan still said he remains "quietly confident" of getting the revised funding plans green lit though, and that the capital was "trying to meet the needs of the government".
The DfT has said it is carrying out a thorough analysis of the business case and Transport for London's updated funding plan to ensure Crossrail 2 is "a robust scheme, as with all transport proposals".
The timeline for the project is particularly sensitive due to its connection to the incoming HS2. Crossrail 2's managing director Michèle Dix said that London cannot cope with the surge of passengers expected from HS2, without Crossrail 2 too.
When Phase 2 of HS2 opens, Crossrail 2 is needed in order to help with the "marked uplift in passengers then arriving at Euston", according to Dix, so the team wants Crossrail construction underway to get it in place for when HS2 Phase 2 is complete.
London's transport bosses want to be given the go-ahead on funding, so a consultation can get underway early next year, with a view to getting the hybrid bill for the project submitted in 2020.