Providing a replacement ferry service at Hammersmith Bridge is a condition of Transport for London (TfL)'s second bailout, the government has said.
The 133-year-old crossing was closed in August after cracks in the structure worsened during a heatwave.
Procurement for a ferry to be used as an alternative route has begun with the service set to start in the new year, government officials said.
The transport secretary said residents had suffered "for too long".
"I'm pleased to say that, following our funding deal with TfL, alongside the excellent work of our Hammersmith Bridge taskforce, this first step is becoming a reality," Grant Shapps said.
The west London bridge is not expected to reopen fully until 2027 and Mr Shapps said he had "also insisted TfL allocate part of the bailout to examining how the bridge can be brought back into use".
A taskforce to reopen the crossing was set up by the Department for Transport (DfT) in October to work with bodies including Hammersmith and Fulham Council, which owns Hammersmith Bridge, and TfL.
Baroness Charlotte Vere, who is chairing the taskforce, said it had "quickly identified a ferry service as the most rapid solution available in the short-term and that's why we made it part of the TfL deal".
The £1.8bn bailout, which will allow TfL to keep Tube and bus services running until March 2021, was agreed last weekend.
David Rowe, TfL's head of major projects sponsorship, said: "Now that TfL has a funding agreement until next March, we are doing everything possible to ensure a ferry is available to get people across the river as soon as possible."
Richmond Council has agreed to contribute up to £375,000 to set up the ferry service, according to the Local Democracy Reporting Service.
However, at a Transport and Air Quality Committee meeting on Thursday night council officers warned the service could not run 24 hours a day due to tidal issues, and it would not be known whether people will be charged to use it or if bikes could travel onboard until the procurement process was complete.
Alexander Ehmann, the committee's chairman, said the council wanted a ferry service "immediately" before the creation of a mid-term solution such a temporary walking and cycling bridge.