The city will halt 21 school construction projects and dozens of other renovations if it does not receive additional education funds from the state, Mayor Bloomberg said yesterday in renewing his push to get Albany to comply with a court order mandating that the state boost funding for city schools by billions of dollars.

The 21 projects would add nearly 15,000 new seats to the city’s public schools.

Mr. Bloomberg put the blame for any delays squarely on Albany. “It’s the state’s shameless shortchanging of our city’s children out of billions of dollars we need for capital school funding,” the mayor said.

Seeking to present a united front in the city’s funding battle with the state, Mr. Bloomberg made the announcement during an appearance with leading education and City Council officials, including the speaker, Christine Quinn, and the head of the United Federation of Teachers, Randi Weingarten.

The dispute centers on a ruling last year in the Campaign for Fiscal Equity lawsuit, in which a state Supreme Court justice, Leland DeGrasse, directed the state to pay the city an additional $5.6 billion a year to ensure that each child receives a “sound basic education,” as required by the state constitution. The state has not acted on the ruling, pending an appeal of the ruling by Governor Pataki.

The mayor said that because last year’s state budget provided no capital education funding, the city advanced $1.3 billion to complete construction projects. The governor’s budget for this year, released last month, also contains no funding for the lawsuit, and the city is refusing to again advance the state’s share – $1.8 billion, Mr. Bloomberg said. “We’ve stretched our available resources as far as they can go,” he said.

The state countered the mayor’s warning about delayed projects by citing Albany’s contribution, through reimbursements, to all city school building projects. “We find this line of argument perplexing because 65% of the costs of each and every school built to approved educational standards is paid for by the state,” a spokesman for the state’s budget office, John Sweeney, said.

City officials, including the mayor, criticized the state’s defense, saying the money reimbursed by the state under the current funding formula was offset by cuts in other areas, forcing the city to increase its operating expenses.

While the state pointed to increases in city education funding in recent years, city officials are focused on the Campaign for Fiscal Equity ruling, which came a year ago today. Both the mayor and the City Council held news conferences yesterday denouncing state lawmakers and Mr. Pataki. The schools chancellor, Joel Klein, and Ms. Weingarten each testified before the council’s Education Committee in a hearing examining the state’s “failure” to comply with Justice DeGrasse’s decision.

In pressing his appeal, Mr. Pataki has contended that the courts shouldn’t determine how the state allocates funds.

In his decision last year, Justice De-Grasse ruled that, after a four-year phase-in period, the state must pay the city an additional $5.6 million a year for operating expenses, such as teachers and books. He also directed the state to come up with $9.2 billion over five years for capital costs, which would include new buildings.

The state’s response to the ruling has infuriated many city education officials and school advocates, and has drawn increasingly heated criticism from Mr. Bloomberg. “Let me ask the elected officials in Albany: What will it take for you to live up to your responsibility?” the mayor said yesterday. “How many more court orders must we win? How many more years will our children be treated as second-class students?”

Seeking to ramp up the pressure on Albany, the mayor tried to enlist the public in his effort. “Call your Assemblyperson, call your state senator, call the governor’s office,” Mr. Bloomberg said, adding that if New Yorkers didn’t have the phone numbers, they could call 311. “Tell them, ‘Enough is enough.’ Enough excuses. Enough politics. Enough sitting on their hands and hoping we will go away.”

The mayor’s statements come a week after his advisers indicated he would cross party lines and back Democratic state Senate candidates that supported the city’s effort to secure more education funding from the state. The report heightened tensions with the Senate’s Republican leader, Joseph Bruno.

Mr. Bloomberg did not single out either Mr. Bruno or the governor for blame yesterday, saying the responsibility for the city’s funding woes was shared in Albany. A spokesman for Mr. Bruno questioned the mayor’s threat to postpone construction projects, saying that while the Campaign for Fiscal Equity lawsuit remained an issue before the courts, state funding for city schools has increased. “There’s really no reason for the city to put off those projects,” the spokesman, Mark Hansen, said.

Construction has not begun on the 21 school buildings the mayor mentioned, but was scheduled to begin this year. In addition to the new buildings, the city’s plans include: 40 new science labs; 15 libraries; 40 arts facilities; 60 athletic facilities; 20 technological upgrades, and 20 new heating systems. Another 68 schools, containing about 38,000 seats, are also “at risk” is the state aid is not forthcoming, the mayor said.

After appearing with Mr. Bloomberg, Ms. Weingarten and Mr. Klein testified before the council’s Education Committee, whose new chairman is Robert Jackson, one of the original plaintiffs in the 13-year-old Campaign for Fiscal Equity lawsuit.

Mr. Jackson noted that his daughter was in first grade when the lawsuit began in 1993; she is now a sophomore at Julliard.

Before the hearing, Mr. Jackson joined education advocates in blasting Mr. Pataki’s education budget and pointing to a poster-size report card that gave the governor all Fs. “We’ve waited too long, and the time for action is now,” Mr. Jackson said.

Despite the mayor’s effort to project unity, not everyone agrees that the city needs more money to fix its school problems. “There’s enough money to run a great school system,” a senior fellow at the Manhattan Institute, Sol Stern, said. “It’s their problem that they can’t do it.” Mr. Stern cited the city’s increased education spending in recent years. “We have thrown more money at the problem, and it didn’t help,” he said. “Upstate taxpayers do not want to foot the bill for what they consider to be still a dysfunctional school system.”