SAN FRANCISCO — California’s $64 billion high-speed rail plan lacks reliable funding sources and is in danger of ending up with only one line that doesn’t connect to San Francisco or Los Angeles, members of a Congressional panel said Monday during a hearing.

Proceeds from a state environment program that is supposed to help fund the project were far below expectations and private funding for the train has yet to materialize, Rep. Doug LaMalfa, a California Republican, said.

“Where is the money going to come from,” LaMalfa asked Dan Richard, chairman of the rail authority’s board.

Richard said private firms have expressed interest in the system but want to see the first leg up and running. That leg between the Central Valley and Silicon Valley is currently under construction and slated to open in 2025.

California voters approved $10 billion in bonds for the project in 2008, and federal officials awarded California $3.5 billion.

The plan is to eventually connect San Francisco with Los Angeles — a trip that officials say would take under three hours on a high-speed train.

“This will operate profitably when we get it done,” Richard said.

Supporters of the rail project have presented it as a cheaper and cleaner alternative to highway construction and airport expansion that would otherwise be needed to meet the state’s growing population.

Congressman Jeff Denham, another California Republican who chairs the House subcommittee on railroads, pipelines and hazardous materials, questioned whether the money for high-speed rail would have been better spent on other infrastructure projects, particularly water projects given the state’s drought. He also expressed concern about funding.

“All of the money is going to be spent and you could be stuck somewhere in a field …, and we’re out of money,” he said.

Sarah Feinberg, administrator of the Federal Railroad Administration, said big infrastructure projects such as high-speed rail encounter challenges but are still worth pursuing.