According to the agency's Web site, only $2.1 billion has been spent.

WASHINGTON—Energy Secretary Steven Chu expressed frustration Thursday that most of the roughly $37 billion in stimulus money Congress gave his agency last year had yet to be spent, but said the agency could manage a new round of funding for clean-energy projects as part of an expected jobs bill.

At a hearing of the Senate Committee on Energy and Natural Resources, Dr. Chu said his agency had handed out only a fraction of the authorized stimulus funds. According to the agency's Web site, only $2.1 billion has been spent.

The disbursement has been slowed partly by the complexity of the review process the department must follow when determining which projects are eligible for support, he said.

Dr. Chu also suggested that state and local governments in the U.S. were having problems coping with the bureaucratic requirements.

"We're not dilly-dallying," he said. "Many of these organizations aren't used to dealing with that magnitude of money."

But some lawmakers are questioning the agency's ability to quickly spend more money.

"How will you spend more when you still have $32 billion that is still hanging out there?" asked Sen. Lisa Murkowski, (R., Alaska).

Some state officials say the delays have not been solely on their end. Massachusetts officials say Dr. Chu's agency took nearly seven months to determine whether the state's proposal to spend $55 million on insulation, window replacement and other projects required a review under the National Environmental Policy Act, a federal law that requires agencies to make sure federally funded projects won't harm the environment.