A group of former transit officials said yesterday it plans to launch a half million-dollar advertising campaign aimed at pressuring state and city elected officials to finance in full the Metropolitan Transportation Agency’s five-year capital plan.

Governor Pataki’s latest budget proposal falls $8 billion short of the $27 billion the MTA requested in its 2005-09 capital plan for subway expansion projects, including the Second Avenue subway, access to the East Side through the Long Island Railroad, a rail link connecting JFK Airport with Lower Manhattan, and an extension of the No. 7 subway line. The budget shortfall would delay those projects and possibly cost the city billions of dollars in federal funds, according to the group, which calls itself the Empire State Transportation Alliance. Among the federal transit aid that could be jeopardized, the group said, is $2 billion in tax credits used to help build a $6 billion rail link connecting JFK airport to Lower Manhattan. President Bush, in outlining his federal budget plan on Monday, urged Congress to approve the use of that money.

The MTA’s five-year, $27 billion capital plan consists of $10 billion for expansion projects and $17 billion to bring the subway system, whose upkeep was sorely neglected until the first capital plan was introduced in 1982, into a “state of good repair.” But exactly how that money will be spent remains unclear. That is one reason why a board that oversees the state-run MTA vetoed its capital budget plan in December.

“We don’t want to give the MTA a blank check,” a spokesman for a key state senator, Dean Skelos of Nassau County, said.

“The MTA,” the spokesman, said, “has never come to us and gone through the entire program to explain to us how they were going to spend the money.”

Mr. Skelos, who is a Republican, and a Democratic assemblywoman of Queens, Catherine Nolan, head the MTA Capital Program Review Board.

Another reason the capital plan has not been fully financed, Mr. Dunham said, is the budget deficit of about $4 billion that the state faces for the fiscal year beginning April 1. The city must close a $3.7 billion budget gap for its 2006 fiscal year.

The alliance, whose leaders spoke at Grand Central Terminal, gave few details on how the state could fill the financing gaps, other than to say it could come from a mix of revenue streams, including taxes, fees, sales of assets, and contributions from the federal government.

Mayor Bloomberg has said the city would pay for the expansion of the No. 7 if the new Jets stadium on the West Side is built. He has not specified where that money would come from.

An attorney for the Straphangers Campaign, Gene Russianoff, who is another member of the alliance, praised the governor for putting “his toe in the water” by calling for increases in Department of Motor Vehicle fees and increasing the mortgage reporting tax. “But he’s got to do better,” Mr. Russianoff said.

The Regional Plan Association, which is a member of the alliance, has pro posed a gasoline tax, but Mr. Pataki has already voiced his opposition to that.

“Businesses will pay, commuters will pay,” the president of Regional Plan Association, Robert Yaro, said. “Everyone who lives in the region benefits from this, so everyone should pay.”

The alliance represents an unusual coalition of groups that have, in the past, found themselves at loggerheads, such as labor and business leaders as well as the Straphangers Campaign, a rider-advocacy group that has been critical of how the MTA is managed. Giving the alliance the gravitas of officialdom were former MTA chairmen Richard Ravitch and Peter Stengl, a former commissioner of the city’s Department of Transportation, Elliot Sander, and a longtime official of that department, Samuel Schwartz.

The alliance came together to support the MTA capital budget in 1999. It spent $125,000 for subway ads that urged commuters sick of riding overcrowded subways to “send the politicians a message loud and clear.”

This year’s print and radio campaigns, which will be led by the group that produced the Straphangers 2002 campaign against the fare hike, Robbett Advocacy Media, will target the city’s subway, bus and commuter train riders as well as drivers upstate, since the group has called upon the governor to finance fully the state Department of Transportation’s budget needs as well.