Senator Schumer is expected to warn business leaders today that $2 billion in federal transportation money could be at stake if the development team charged with rebuilding Lower Manhattan does not settle on a plan and begin construction soon.

Mr. Schumer’s office told reporters late Monday that he will deliver an ultimatum on spending the federal money at a breakfast arranged by Crain’s, the business weekly, in Manhattan. The senator is also expected to outline a plan for reviving downtown development, following a spate of reports in recent weeks that the project is in disarray.

Governor Pataki, who said in November that construction on a new foundation at the site would begin three months later, said yesterday that delays were expected because of the large number of parties involved in the process and the complex security issues connected with the site. He did not offer a revised deadline to reporters who pressed him on the matter at the state Capitol.

The governor defended the New York Police Department against complaints, including some that reportedly came from his own staff, that it was slow to issue security guidelines for redevelopment at the World Trade Center site. Calling the department “the best in the world,” Mr. Pataki declined to say whether he personally thinks the department waited too long.

“I’m going to continue to look forward,” Mr. Pataki said. “I’m going to look forward. I believe in solving problems.”

Yet the questions surrounding Lower Manhattan development are not likely to go away soon for Mr. Pataki, who views the project as a defining one for his tenure as governor. That was made clear yesterday by the speaker of the Assembly, Sheldon Silver, a Democrat who represents the area. Mr. Silver blamed the delays on Mr. Pataki and Mayor Bloomberg.

Speaking at a press conference soon after the governor, Mr. Silver said the two Republicans had taken their eyes off development in Lower Manhattan because of a preoccupation with a proposed stadium on the far West Side of Manhattan. Mr. Silver, who will cast a deciding vote on the stadium, has taken every opportunity in recent weeks to criticize Messrs. Pataki and Bloomberg for the slow redevelopment of downtown.

“We are three-and-a-half years after September 11 and they have both collectively failed to recognize the importance of the leadership that is necessary to redevelop downtown Manhattan,” Mr. Silver said. “And all the speeches that were made about showing terrorists that we will rebuild New York bigger and better just went by the wayside as they failed to coordinate a cohesive development plan that really meant development.”

The chorus of complaints continued later in the day as the head of a civic group that has opposed public subsidies for commercial development, Robert Yaro, called for revisiting the development process altogether. Mr. Yaro, president of the Regional Plan Association, made his comments following the announcement that the head of the Lower Manhattan Development Corporation, Kevin Rampe, is resigning.

And they came the same day NY1 News reported that Messrs. Pataki and Silver are considering a plan to kick out the leaseholder of the World Trade Center site, Larry Silverstein, and take the $4.5 billion in insurance money he received following its destruction in 2001. The news station said officials might invoke eminent domain to override Mr. Silverstein’s lease.

Mr. Silverstein recently said he hopes to draw on public funds to finance security features at the site, a plan Mr. Bloomberg has brushed off. Mr. Yaro has expressed skepticism for months over the commercial prospects in Lower Manhattan, saying tenants will be harder to find than Mr. Silverstein and others have let on.

Despite the cascading doubts, Mr. Pataki remained upbeat, saying delays should not be a surprise and he is not worried about the project’s potential impact on his legacy.

In his breakfast talk today, Mr. Schumer was expected to detail his concerns that the city would lose $2 billion in federal transportation aid if “more time is wasted” on a proposed rail link between Lower Manhattan and John F. Kennedy International Airport – a project dear to Mr. Pataki.

Mr. Schumer, who until last fall had been viewed as a likely Democratic candidate for governor next year, also was to discuss his plans to make Governors Island an international biotechnology center, to create an “apron park” around the downtown waterfront, and to urge the state to redevelop other parts of ground zero before construction begins on the 1,776-foot-tall Freedom Tower.