The fight to lure the National Science Foundation -- and it's 2,000 employees and $7 billion annual budget -- out of Arlington County is heating up, with several Northern Virginia communities maneuvering to become the agency's new home.

The General Services Administration, the federal government's real estate manager, this month pushed back the deadline for the foundation to move into a new facility to 2016, a two-year delay that will give builders time to construct a new headquarters.

The extension means that sites along Metro's nearly completed Silver Line -- including Tysons, Reston and Herndon -- will be available to compete for the science foundation, whose lease in Ballston expires next year.

Fairfax County officials, however, declined to discuss whether they will enter the bidding.

Still, it is now a "wide-open competition" for Northern Virginia sites that can provide cheaper space for the agency, said Mark Jinks, Alexandria's deputy city manager.

"We expect that there will be many sites in Northern Virginia that could meet the [foundation's] specifications and might submit proposals," he said.

Alexandria officials have been among the few to publicly express a desire to coax the foundation out of neighboring Arlington. They've already identified at least two sites along Eisenhower Avenue -- Hoffman Town Center and Carlyle Plaza -- that could serve as the agency's new home.

Jinks said both locations meet the foundation's most recent set of site requirements, including 690,000 square feet of office space and access to enough hotel rooms to accommodate 60,000 annual visitors. The sites also provide access to interstate highways and Ronald Reagan Washington National Airport.

"Alexandria would be a great choice for NSF because ... [of the] history and ambience of historic Old Town, which can provide NSF employees and its visitors dining and shopping options [and] a wide range of housing options in regard to lifestyle and affordability," Jinks said.

Arlington County officials remain confident that the foundation will stay in its Ballston home. Even Rep. Jim Moran, D-Va., and Democratic Sens. Mark Warner and Jim Webb put their support behind the Ballston site, writing in a joint letter that a move out of Arlington would have a "detrimental effect" on the area.

"The synergy that exists in our technology hub in Ballston is what makes Arlington so desirable to tech companies, and the NSF is the foundation of that synergy," said Cara O'Donnell, a spokeswoman for Arlington Economic Development.

Communities have until Jan. 9 to submit proposals to the federal government.