(TNS) — The Federal Transit Administration has put the brakes on a $647 million grant to help pay for electrification of a commuter train system on the San Francisco Peninsula that was considered a key part of extending California's planned high-speed rail line to the Bay Area.

The federal agency's move to defer a decision on the grant agreement that had been reached with the Obama administration comes weeks after Republicans in California's congressional delegation asked U.S. Transportation Secretary Elaine Chao to pull the plug on the grant.

The deferral stands to considerably delay plans to convert Caltrain tracks between San Francisco and San Jose from diesel-fueled trains to an all-electric system — and throws a kink into long-term plans by the California High-Speed Rail Authority to have its bullet-trains share improved and electrified Caltrain tracks starting in the mid-2020s.

Caltrain reports that its system carried an average of more than 60,000 passengers a day on weekdays, and more than 19.2 million in 2016.

In a letter Friday to Caltrain Executive Director Jim Hartnett, FTA chief Matthew J. Welbes said the deferral "will allow the project to be considered in conjunction with the development of (President Donald Trump's) fiscal year 2018 budget."

Hartnett had argued in a public statement issued last week that "time is of the essence" for the new Trump administration to approve the grant. "Last year, Caltrain awarded contracts to advance work on the project, but construction cannot start without the investment that is awaiting approval by the new administration," Hartnett wrote. "For the project to move forward as planned, the administration must approve the grant prior to March 1. Any delay would result in costly penalties and cost increases that may threaten the viability of the project."

California's Republicans in the House of Representatives, however, sought to derail the Caltrain grant as a means of blocking the state's bullet train effort — which they have uniformly opposed over the past few years — until the federal government conducts an audit of the high-speed rail project. Substantial construction of the first segments of the high-speed rail system is underway in Fresno and Madera counties.

Caltrain had hoped to receive its first allocation of the grant funds this month to begin work on the electrification project. "However, the considerations described above require additional time to complete review of this significant commitment of federal resources," Welbes wrote.

The federal grant, if it is ultimately awarded, would be matched by another $1.3 billion in local, state and regional investment, including funds from the high-speed rail agency. Caltrain reported that electrification of the system has been part of its long-range goals since the 1990s.

(c)2017 The Fresno Bee (Fresno, Calif.)