Comptroller William Thompson Jr. is urging the Metropolitan Transportation Authority to hold off on plans to defer $2.7 billion of its current capital program to later years, saying it should wait for the findings of a commission that is studying long-term solutions to the agency’s budget woes.

The Ravitch Commission on MTA Financing, formed by Governor Paterson and headed by a former MTA chairman, Richard Ravitch, is scheduled to release its findings in December.

During a rally at Union Square yesterday, and in a letter to the MTA chairman, Dale Hemmerdinger, Mr. Thompson said he is particularly concerned with the idea of delaying a $366 million project involving smoke-removing fans for subway tunnels. He said the deferral would jeopardize rider, worker, and firefighter safety.

“The problem is they are being deferred into an unknown future,” the chief attorney for the Straphangers’ Campaign, Gene Russianoff, said.

He added that delaying $2.7 billion of improvements simply means less money would be spent on the next round of proposed capital projects.

The original 2005-09 capital budget called for $21 billion in improvements.

In response to Mr. Thompson, the MTA released a statement yesterday saying the proposed deferrals “were chosen because they can be delayed without impacting the safety of the system.” The agency also said it would amend its deferrals if the commission identified funding for them.

In addition, the MTA is trimming its own expenses as part of its plan to close next year’s operating deficit, which could reach as much as $500 million. In an internal memo, the executive director and CEO of the MTA, Elliot Sander, instituted several “belt tightening” measures, including a freeze on employees’ out-of-town travel not involving procurements, a 60-day delay for new hires, and the elimination of food and beverage service.

The MTA on July 23 is scheduled to announce its preliminary financial proposal for the next four years.