When the Assembly speaker, Sheldon Silver, helped block a Jets stadium on the far West Side, he said he was worried that it would compete with the rebuilding of Lower Manhattan, a project he has called a moral imperative.

A fellow Democrat, Senator Schumer, is among those who hope that another project, the expansion of the no. 7 line from Times Square to the Jacob K. Javits Convention Center, will do as much as a stadium to stimulate growth on the West Side.

Mr. Schumer weighed in on the development of the far West Side with a policy speech yesterday, arguing that the $2.1 billion no. 7 extension was the linchpin in the development of the neighborhood, a magnet that would lure businesses to the area without tax breaks offered under earlier plans proposed by Mayor Bloomberg.

“Once developers believe the no. 7 line expansion is for real, they will flock to the area,” Mr. Schumer said during a speech sponsored by a group representing the business and investment communities, Partnership for New York City.

Though the state’s senior senator took pains to say development would not come at the expense of downtown’s rebuilding efforts, such assurances may not comfort Mr. Silver, who has argued that development of Lower Manhattan should take priority.

The proposal to expand the no. 7 line is part of the Metropolitan Transportation Authority’s $21.1 billion capital plan, which is now being reviewed by a four-member board in Albany, which includes representatives of the governor, the leaders of the state Senate and Assembly, and the mayor, whose proxy votes only on issues regarding the subway and city buses.

Mr. Silver can again shape the future of the West Side development through his representative on the Capital Program Review Board, an Assembly member from Queens, Catherine Nolan. But it is unclear if the proposal for the extension must remain in the capital plan since the city has proposed to finance it, a spokesman for the Senate representative on the board, Dean Skelos, a Republican of Long Island, said.

“There is a difference of opinion on whether the Capital Program Review Board has to approve it since city is paying for it,” the spokesman, Tom Dunham, said.

Unable to win passage of the plan by the review board last month, the MTA resubmitted its capital plan at the beginning of June. The board has 30 days to pass the plan unanimously – though mass-transit activists, for the sake of momentum, are hoping for an outcome by the time the legislative session ends June 23. If the capital plan is not passed within 30 days, the plan can be resubmitted.

Much of the current impasse over the plan revolves around how the limited resources for expansion projects can be divided. The MTA asked for $27.8 billion for its 2005-09 capital plan, saying $17.2 billion was for its “core program” of maintaining existing facilities with about $10 billion to be spent on expansion projects. The state authorized $21.1 billion, and it is likely that expansion projects will compete for about $4 billion.

A spokesman for Mr. Silver, Charles Carrier, would not say how Ms. Nolan would vote, but he did make clear that priority should be given to areas where the subway was consistently overcrowded – notably the Lexington Avenue line, which absorbs 40% of the subway system’s daily ridership. Crowding on that line would be relieved by the planned Second Avenue subway line, which would run from East Harlem through the Upper East Side south into Mr. Silver’s district.

“The speaker does not disagree with Senator Schumer about expansion,” Mr. Carrier told The New York Sun. “The priority for the speaker is Lower Manhattan.”

Aside from the Second Avenue subway, Mr. Silver has favored East Side Access, a planned project to bring the Long Island Rail Road to Grand Central Terminal.

“Some areas have a crying need right now,” Mr. Carrier said. “You have to address those overcrowded conditions now because that is where you have a problem.”

The two-track, 7,000-foot extension of the no. 7 would provide access to the 790,000-square-foot Javits Center, which Mr. Schumer said yesterday should be expanded to 3 million square feet, almost twice as much as the 1.75 million square feet originally proposed as part of Mr. Bloomberg’s redevelopment of the West Side.

The senator said the money the city would save by not offering tax breaks could be put toward paying for any cost overruns incurred if the no. 7 line is built, and a hotel tax could be proposed to cover additional overruns. Who would pay for cost overruns has been an issue since the mayor offered to finance the extension as part of his proposal to build a stadium on the West Side.

“As far as I’m concerned, the no. 7 line is the subsidy for that development, and West Side developers should pay full fare,” Mr. Schumer said.

The no. 7 line has long been criticized by transit activists as a distraction from the MTA’s more pressing needs, such as station rehabilitation and the Second Avenue subway. Yesterday, mass-transit advocates protested the cancellation of 12 scheduled station rehabilitations, at a cost of $400 million.

“Right now, the Second Avenue subway is more meritorious,” a senior attorney with the advocacy group the Straphangers Campaign, Gene Russianoff, said. “The issue is one of priorities.”