* Current law prohibits US from transit safety role

* Deadly DC crash, other accidents prompt move

WASHINGTON, Nov 15 (Reuters) - The Obama administration plans to propose that the U.S. government oversee safety for subway and light rail systems, a move prompted in part by the deadly collision of two trains in Washington this year.

According to a draft of the plan to be formally unveiled in coming weeks, the Transportation Department would either enforce safety regulations itself or grant states the option to do so under its guidance and financial assistance.

No cost estimate was provided and Congress would have to approve the proposal.

The administration has concluded that the government's ability to insure transit safety is weak at a time when ridership is increasing and state budgets for maintaining and enforcing their own regulations are tightening.

State agencies responsible for transit safety often have few staff, little expertise, inadequate independence from transit systems they oversee and limited legal authority, federal officials said.

A 1965 law prohibits the federal government from overseeing safety regulations for subways. At the time, there were only a few systems nationwide.

New York, Chicago, Los Angeles, Washington and Boston have the five largest public transit systems in the United States. They accounted for more than half of the 10 billion passenger trips in 2007, according to the latest industry statistics.