The New York Cosmos soccer team said it will begin "seriously exploring" alternative sites for a proposed 25,000-seat stadium, hotel and retail complex at Belmont Park if the state doesn't decide on the $400 million project before the end of the year, team officials said Tuesday.

In February 2013, the Cosmos -- along with three other companies that have proposed retail and recreation complexes at the Belmont site -- submitted bids with Empire State Development, the state's primary economic development agency, to build on the state-owned property in Elmont. The state has yet to choose a bidder.

"It's frustrating to be in this situation," Erik Stover, CEO of the Cosmos, said in an interview Tuesday. "We are at a point where we are running out of time. Any business trying to grow and trying to build itself needs to in fact grow. If you are staying flat or neutral, you are falling behind."

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Stover said if the state does not make a decision on its bid by year's end, the team will conduct a financial analysis of several other sites on Long Island and in Queens, Brooklyn, Westchester and New Jersey. He declined to identify them.

Jason Conwall, an ESD spokesman, said the agency "continues to review and consider all responses."

The Cosmos, which had been one of the most popular American teams in the 1970s before folding in 1985, restarted in 2012 in the North American Soccer League. The league is considered a step below the more established Major League Soccer. For the past three years, the Cosmos have played at Hofstra University's James M. Shuart Stadium.

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The team has spent millions of dollars responding to the state's request for proposals, and on lawyers, architects and project designers, Stover said. He said the team has also been unable to sign high-profile players because the club does not have a permanent home.

"The opportunity costs have been enormous," Stover said.

The Cosmos want to build a stadium, 175-room hotel, nine restaurants, a community center, retail stores, movie theater and a 4.3-acre public park. The club also said it will spend $2 million to build and refurbish soccer fields across the county.

Construction would take about 2 1/2 years.

The project has the support of Nassau County Executive Edward Mangano, state Sen. Jack Martins (R-Mineola), Rep. Kathleen Rice (D-Garden City) and numerous civic leaders.

Nassau County Legis. Carrié Solages and his sister, Assemb. Michaelle C. Solages, both Democrats from Elmont, are leading the opposition to the Cosmos' plans at Belmont. They say the area needs a grocery store and affordable housing.

In April, the Cosmos played at Coney Island's MCU Park -- home to the Brooklyn Cyclones minor league baseball team -- and Stover said the borough is a "potential" long-term home for the team.