ALBANY – Governor Pataki launched an aggressive backroom push late Tuesday for a law that would allow for an unlimited number of charter schools in New York City and raise a statewide cap on the independent public schools to 200 from the current 100 limit.

Lawmakers said Mr. Pataki told leaders in the Democratic-led Assembly that lifting the cap on charter schools would be a top priority for him going into the final two days of the legislative session, triggering negotiations that are expected to result in a change to the current law.

The last-minute negotiations are opposed by the chairman of the Assembly education committee, Steven Sanders, a Democrat of Manhattan, but could go through against those protests if the speaker of the Assembly, Sheldon Silver, also a Manhattan Democrat, is faced with a difficult choice between bills his members want and a stubborn Mr. Pataki.

“At some point when we reach the cap, I have no doubt we are going to address the issue,” Mr. Sanders said. “But at this point, we have no plans to lift the cap before we reach the cap. We’re not going to raise the 100-school cap.”

The substance of the negotiations between Mr. Pataki and the Legislature was not made public yesterday. But people close to the talks, speaking on condition they would not be identified, said the governor has threatened that unless changes to the charter school law are made, he will veto bills that direct money to upstate school districts, a number of which passed in the Assembly this week.

“We know it’s being discussed,” Senator Martin Golden, a Republican of Brooklyn, said. “And I would daresay that if this is one of his top issues, there will be some movement.” He is the lead sponsor of a bill that would lift the cap statewide.

Mr. Pataki convinced lawmakers to allow charter schools in New York seven years ago, in exchange for a legislative pay raise. There was some speculation yesterday that another pay hike would be offered in exchange for raising the cap, but aides to the governor said such a deal was not on the table as of late in the day.

Speculation about a deal began Tuesday night as charter-school lobbyists gathered outside the Assembly chamber. Opponents of charter-school expansion surfaced at the Capitol the following morning with literature aimed at discrediting the schools. The appearance of lobbyists on both sides suggested a deal was in the works.

“The fact that we haven’t seen a bill yet means nothing,” a spokesman for the New York State School Boards Association, David Ernst, said. “The first charter-school act didn’t surface until the last minute and was passed and signed into law before the general public had any awareness of what was in it. We’re very much concerned that this same sequence of events might be occurring this year.”

His group is leery of charter schools, which it sees as siphoning off resources and good students from traditional public schools.

According to multiple sources, Mr. Pataki’s staff agreed Tuesday to press both for an exemption in New York City to the cap – as Mayor Bloomberg and his schools chancellor, Joel Klein, had avidly sought – and for raising the cap statewide to 200 from 100. The governor’s original charter-school proposal in 1998 called for an unlimited number of the schools.

Advocates of charter schools worry that communities looking to establish the schools will be shut out this year because of the dwindling number of available openings. There are currently 61 operating charter schools in the state, including 32 in New York City. At the beginning of the coming school year, the number will increase to 79. Of the 18 new schools, 14 will be in New York City.

The executive director of the Charter Schools Institute of the State University of New York, James Merriman, said he anticipates that institutions authorized to issue charters will soon be turning applicants away.

“I would expect us to be at a point where we have extremely strong applications coming in from across the state this fall and we will not be able to give charters to them, and I imagine the Regents will be in the same position,” Mr. Merriman said.

Changing the current law on charter schools this year would almost certainly require the governor to issue an order to the Legislature, or a “message of necessity,” directing it to pass a law without the ordinary three-day waiting period after the introduction of a bill. It was widely thought Mr. Pataki would not issue messages of necessity this year, but aides sent signals yesterday that he would.

“This is going to come out of negotiations,” a person familiar with the negotiations, who asked not to be identified, said. “If they have an agreement, they will find a way to make it happen.”

Mr. Pataki acknowledged in a press conference late yesterday that, in the rush to the end of the session, he is looking to expand the cap. One reason the issue may have moved to the top of his agenda was the emergence in recent months of a number of outspoken upporters among Democrats, particularly from New York City.

Assemblyman Ruben Diaz, a Democrat of the Bronx, said the governor was impressed, at a meeting in his Albany office last week with the 44-member black and Hispanic legislative caucus, by the level of support for charter school expansion. The point was underscored again Monday when a Democratic senator from Queens, Malcolm Smith, walked from the Senate chamber to the Assembly to lobby Mr. Sanders on the issue. Mr. Smith, who has two charter schools in his district, said he hopes the cap will be lifted after Mr. Pataki’s intervention.

“I think we’ll get some increase in the cap now that the governor has weighed in very clearly on this,” Mr. Smith said. “He’s the governor, no matter what anyone says. It means something. And there’s always something to give up. There’s always a trade.”