A long-awaited redevelopment project in the heart of Springfield is on hold indefinitely in what may be the first large-scale casualty of Fairfax County’s flattened housing market.

Midtown Springfield, a proposed 9-acre cluster of dwellings, shops and offices, was an integral part of a plan to revitalize the lackluster area. Last year, an attorney for developer KSI said the project could be under way by late 2007.