Local transportation agencies such as the Los Angeles County Metropolitan Transportation Authority rely in some part on federal funding to run and build transit.

So when the Trump administration delayed a federal grant that was set to go to the Caltrain system in Northern California last month, it rattled some officials here.

California Republican congressional members wrote a letter to the administration to oppose the $647 million grant, which would have helped convert the busy Bay Area railway from diesel to electric. But because it would fund improvements related to the state's controversial high speed rail, the Republicans raised objections.

The move to delay and potentially block the funding was one of the first big moves by new U.S. Secretary of Transportation Elaine Chao, and it signaled a change in priorities for the department under the new administration.

Last year, federal funds amounted to about 18 percent of L.A. Metro’s budget. Those dollars paid for nearly half of Metro’s big projects — the Purple Line subway and Regional Connector included.

Much of those funds came by way of discretionary grants decided by the U.S. Department of Transportation. Limited funding for operations and maintenance is provided through a federal transportation bill passed by Congress in 2015, which doesn't expire until 2021.

Metro CEO Phil Washington said he’s still optimistic his agency will continue to get federal funding, especially in light of the passage last year of Measure M, the county sales tax increase to pay for transportation projects.

"We think that federal funds will come our way because we have invested in ourselves," he said. "We’re not coming empty handed to the federal government. We have funding to match and to leverage."

But other Metro officials have expressed doubts about future funding, especially for projects related to high speed rail.

Last month, the board voted to delay a redesign of the Union Station tracks and concourse because construction funding has not been secured. Some of the funding would be provided by county sales tax measures, but the bulk is expected to come from the California High Speed Rail Authority and potentially federal grants.

"I love the plan," said Sheila Kuehl, Metro board member and county supervisor at the board's February meeting. "But it it looks to me like we're making some pretty large assumptions about what we might get from high speed rail ... and that seems iffy to me."