For months, the City Council speaker, Gifford Miller, has managed to avoid taking a stand on the controversial football stadium being proposed for the far West Side of Manhattan.

At a speech Thursday in front of a consortium of construction groups, however, Mr. Miller is expected to break his silence. Sources said his position will sound a lot like what the city comptroller, William Thompson Jr., and the Independent Budget Office have already said.

Rather than blasting the idea of a stadium, which is being fervently pushed by the Bloomberg administration, Mr. Thompson and the watchdog agency criticized the proposal’s financing and said there were flaws in its economic projections.

Mr. Thompson, a potential opponent of Mr. Miller’s next year for the Democratic nomination to run for mayor against Mr. Bloomberg, called the mayor’s proposal for redeveloping the area occupied by the Hudson Yards “extremely risky.” He also said the reliance on a quasi-independent entity, called the Transitional Finance Authority, could create fiscal problems and could reduce accountability.

“Your proposal calls for an unprecedented use of the Transitional Finance Authority to commit to what has been deemed an investment in a project that could yield little return to City taxpayers and may in fact cost them billions of dollars,” Mr. Thompson wrote to the mayor last month. “The Hudson Yards financing mechanism creates a troubling and inappropriate precedent with potential impact beyond this project.”

The Independent Budget Office said the project will create half the jobs and less tax revenue than predicted by the Bloomberg administration and the owner of the New York Jets, but it predicted that even the reduced tax revenue would cover the city’s annual $21 million debt service.

For Mr. Miller, as a prospective candidate for mayor, straddling the issue leaves some wiggle-room, ensuring that he does not alienate those Manhattan residents who are adamantly opposed to the plan or close the door on the construction workers’ unions who strongly favor it.

And though Mr. Thompson is said to be in the pool of Democrats considering a mayoral run, many predict the comptroller will back out to stay in his current job, which would leave his stance available for Mr. Miller to run with in a primary.

Mr. Miller’s chief spokesman, Stephen Sigmund, declined to comment last night, saying the speech was not even written. Sources who did not want to be identified said, however, that Mr. Miller will outline his concerns while leaving open the possibility of a stadium.

They did point out that he had been seriously contemplating it for sometime, knowing it could emerge as a prominent issue during the 2005 campaign and recognizing that the City Council will have to approve rezoning the area for the project to go forward.

In April, Mr. Miller said he favored rezoning the largely industrial neighborhood but would take a position on the stadium only in July – which he did not. “I am not reflexively opposed to a stadium for that site,” Mr. Miller was quoting as saying by Crain’s New York, which was host of the breakfast where he delivered his remarks, “but I have a lot of concern about public investment of $300 million.” That would be the city’s share of the stadium.

The Jets stadium, a 75,000-seat domed arena that its advocates call the New York Sports and Convention Center, has become the sticking point in the expansion of the Jacob K. Javits Convention Center. The $1.4 billion stadium project requires not only the city, but also the state, to pay $300 million to build a platform over the existing rail yard and a retractable domed roof on the arena. The Jets would kick in the remaining $800 million. The city would also issue about $2.8 million in long-term bonds and $900 million in short-term commercial paper borrowing.

Mr. Bloomberg argues that the finished project, which includes both the stadium and an expansion of the existing Javits Center, will pay for itself and will spur the economy with added jobs and revenue. He and Deputy Mayor Daniel Doctoroff are using the stadium as the linchpin for the city’s 2012 Olympic bid.

Mr. Miller has managed to duck the issue, even as it has generated intense publicity. Last week, the mayor and Cablevision, the owner of Madison Square Garden, went to verbal war when the telecommunications giant launched a series of television commercials blasting the city for trying to spend millions of dollars in taxpayer money on a stadium in a period of fiscal peril.

Mr. Bloomberg struck back again yesterday in his weekly radio address, saying Cablevision is out to “destroy” the city’s Olympic bid.

“There is no lie they are not willing to tell,” the mayor told his listening audience. “They have tried to scare New Yorkers into believing that they face a choice between the stadium and essential city services, like education and public safety, even going so far as to suggest that high subway fares could result. None of these things are true.”