Developers are scrambling for the opportunity to build Loudoun County's first regional shopping center. Owners of potential sites in the eastern part of the county have talked with developers about joint ventures and possible sell-outs.

Those interested in guaranteeing themselves the right to try to build a shopping center designed to keep increasingly affluent Loudoun shoppers from spending their dollars in Fairfax County are lobbying Loudoun officials and future fellow business leaders. One potential developer already is talking with possible tenants.

Some of the biggest names in the Washington development business are involved, including Theodore Lerner, Michael Hadid and Alan Kay.

The battle centers on a small area near Washington Dulles International Airport. The potential sites are less than five miles apart. Both are along the Rte. 28 corridor. One faces Rte. 7. One of the sites is zoned for a regional mall. Both are within five miles of the site of the planned state Center for Innovative Technology.

* Lerner, developer of major shopping centers throughout the Washington area, has brought in Southmark, a Dallas-based land investment company, to help develop a 600,000-square-foot mall at the intersection of Rtes. 28 and 7 between Sterling Park and Leesburg. The project, known as Windmill, has been in the planning stages for years. In 1980 the Virginia Supreme Court upheld a 1975 decision by the Loudoun County Board of Supervisors denying an application by Lerner to build a regional mall on the site in spite of a 1969 land plan that labeled it for future development as a regional center.

Attorney Tom Nalls said his clients have filed a new application for a mall on the same site. He said the land already is approved for an office park.

A spokesman for Southmark did not have details of that company's involvement in the Loudoun project, and Dave Morgan, the man in charge of shopping center operations for the company, was out of town.

* Hadid, head of Hadid Investment Group in Rosslyn, has a major interest in the development of a regional shopping center almost in the shadows of Dulles Airport fronting on Rte. 28. According to preliminary plans, Hadid would make major contributions to road improvements in the area, including widening a stretch of Rte. 28 from two to four lanes.

According to a company spokesman, Hadid has the 72-acre site "under contract" and has been developing plans for a 600,000-square-foot mall two miles south of Rte. 7 and about a mile from the Lerner/Southmark site. However, the site Hadid said he wants to develop is owned by Nattak Development Co., which is owned by Kay of the building firm of Rozansky & Kay.

In December, the Loudoun Board of Supervisors approved rezoning for Nattak's planned shopping mall and 400,000-square-foot office-space development on the same site.

Kay said Thursday that he is "having discussions about the site" with Hadid, but added that nothing is final. "There is a lot to be concluded," Kay said.

There is also the possibility of a joint venture between the two, according to sources.

Hadid said the property is definitely "under contract," but explained that the contract contains contingencies and allows for "a study."

Anything final is months away, Kay said.

That should give both of them the chance to see if Loudoun County is going to approve the Lerner/Southmark proposal. According to the Loudoun County Planning Department, public hearings on the proposal have not yet been scheduled.

Nalls said the Lerner land is situated at the "confluence of the major traffic arteries in eastern Loudoun."

One commercial developer predicted that the race to build a regional mall would quickly become a race to see who can sign up major tenants first if Loudoun officials end up approving the Lerner site.

Kay said he already is talking with potential major tenants. Even though Hadid and Kay have not settled on Hadid's long-range future in the development, Hadid visited Loudoun County officials last week. A spokesman said that Hadid does not want to be rushed into putting "concrete in place. We don't want to fast-track anything."

Hadid said he does not want to get into "any horse race with Lerner."

Recently, Hadid said he did not "want to build an inferior product." He said he wants time to build more than just a shopping center. He plans to include "lots of amenities, including a professional school, community parks and a medical center."

Several other developers have said that a computer training center will be needed in the future to help train support staff for the increasing number of high-technology firms moving to facilities along the Dulles toll road. That reportedly is what Hadid is proposing.

Southmark's investment in the Lerner project marks the Texas company's second Loudoun County venture in the past year. Southmark purchased a major portion of the old CSX Minerals site along Leesburg Pike near the Countryside residential development several months ago.