The state will sell off a large parking lot to help pay for the expansion of the Jacob K. Javits Convention Center. The sale of the lot, which covers an entire city block, will generate an estimated $339 million, the state said yesterday.

The space – once designated to be parkland as part of the failed West Side Stadium project – will be sold for commercial and residential development.

The announcement came at the unveiling of the first design plans for the $1.7 billion convention center expansion, which the state hopes to begin by late this summer and complete by 2010. Previously, the state said the plan would cost $1.4 billion.

The expansion will extend the convention center north along Eleventh Avenue one block to 40th Street, and will increase exhibit and meeting room space to more than 1.3 million square feet. The state said meeting space would be increased five-fold and convention space by about 45%.

The chairman of the state’s development agency, Charles Gargano, said the state is working with the city Planning Commission to prepare for the sale of the lot on Eleventh Avenue between 34th and 35th streets in coordination with the city’s Hudson Yards redevelopment plan.

Yesterday, the state also announced plans to build a convention center hotel across Eleventh Avenue from the entrance to the Javits Center between 35th and 36th streets. The site was chosen, according to Mr. Gargano, in part because it is already controlled by the convention center, saving about $150 million that was budgeted for hotel site acquisition costs.

A representative of Tishman Construction, which will oversee the hotel construction, said yesterday the state would soon issue a request for proposals for private development of the hotel site, to be built at the same time as the Javits expansion.

A general project plan will be published next month, based on the designs released yesterday. That plan must gain approval from the state development agencies and the Public Authority Control Board; a panel controlled by Governor Pataki; the Senate majority leader, Joseph Bruno, a Republican of Brunswick, and the Assembly speaker, Sheldon Silver, a Democrat of Manhattan. That board blocked the Bloomberg administration’s West Side Stadium project in June.

Should the expansion plan move forward, the city would contribute $350 million and the state $350 million, in addition to selling off the 34th Street property. An additional $645 million would be made available from bonds backed by a $1.50 a key surcharge now being charged by city hotels.

The state estimates that the Javits expansion will bring an estimated $53 million in combined annual tax revenue for the city and the state and create thousands of new permanent jobs.

In December, Assemblyman Richard Brodsky, who heads the Committee on Corporations, Authorities and Commissions, held a public hearing during which he questioned Mr. Gargano on the slow pace of the expansion and potential cost overruns.

After reviewing the new designs yesterday, Mr. Brodsky, who is running for attorney general, told The New York Sun, “It’s very hard to understand why we should invest $2 billion for a facility that is not dramatically better than the one we have now. This plan does not work for the New York business community. You are paying too much for too little.”

Mr. Brodsky vowed soon to reopen the expansion plan hearings.

At the December hearing, Assemblyman Richard Gottfried, a Democrat, asked Mr. Gargano to consider alternative Javits expansion plans preferred by two advocacy groups. One plan, advocated by developer Douglas Durst, would expand the convention center south over the rail yards that were once earmarked to be the site of the West Side Stadium. The other plan, advocated by the Steven L. Newman Real Estate Institute, would demolish the current convention center and build a new one over the rail yards on an east-west axis, which advocates said would open up the Hudson River waterfront.

A state official who has overseen the Javits expansion plans, Michael Petralia, said yesterday that the state had met with Mr. Durst and would meet with representatives of the Newman institute. But Mr. Petralia said that escalating construction costs and all of the work and money invested in the current plan mean that the state would move forward with its existing plan.

At a press conference at the state’s Midtown offices yesterday, a Pritzker prize-winning British architect, Richard Rodgers, presented the expansion plans. He said his designs are intended to humanize the Javits center, which he said is “more like a black mausoleum than a great exhibition space.”

Mr. Rodgers said the designs, which he drew up in conjunction with Fx-Fowle Architects and A. Epstein & Sons, are also aimed at creating more public space along Eleventh Avenue and to act as a catalyst for the restoration of an underdeveloped neighborhood.

The design features a tree-lined colonnade along Eleventh Avenue and a small park on the avenue between 39th and 40th streets. A 100-foot-tall glass facade would run for about 1,000 feet along Eleventh Avenue. Mr. Rodgers said the new space should attract cafes and restaurants.

Mr. Rogers’s past projects include the Millennium Dome in London and the Pompidou Center in Paris.

The expansion plans are termed “Phase 1,” and the designs described yesterday allow for further expansion of the center to the north.

Even after the first phase of the planned expansion, New York’s convention space will be much less than the square footage of other major American cities. McCormick Place in Chicago, for example, will be the country’s biggest center at 2.9 million square feet after an ongoing expansion is completed.