The US transport department will provide $171m towards San Francisco's Transbay Transit Center project, which will link high-speed rail and commuter trains in the state of California.
The loan will fund 14% of the first phase of the total $4.2bn multi-story intermodal facility to link nine transit systems, including bus and rail, and centralise the state's transport network.
The first phase involves replacing the existing Transbay Terminal with the new modern transit hub and is scheduled to begin this spring and finish by 2014.
The second phase, involving a 1.3-mile extension of Caltrain (the California commuter rail line) tracks to the new terminal, is scheduled to finish around 2016. Linking San Francisco and southern California with high-speed rail is scheduled to finish by 2020.
The terminal is expected to serve over 45 million passengers annually and boost public transportation, reduce congestion and cut CO2 emissions.