Residents of the Tysons Corner area will attempt tonight to block developers' plans for what they charge would be a $100-million, 20-story "visual intrusion" on their Fairfax County homes.

The developers who are asking the Fairfax Board of Supervisors to approve their proposal say they prefer to call the mirror-surface twin high-rises, which would provide the highest points in the Fairfax skyline, a "community landmark."

"We've got the Marriott and the Ramada Inn," said Lilla Richards, president of the Fairfax Federation of Citizens Association and an outspoken opponent of the high-rises. "There's no overwhelming, compelling public need for a landmark."

The buildings would tower above the existing commercial skyline near the Tysons Corner Shopping Mall and would be almost twice as high as current zoning regulations allow. The two office buildings would be constructed on either side of the Tysons Marriott Hotel between Tysons Corner Shopping Center and the Capital Beltway.

After two years of controversy and negotiations, the proposed Tycon Towers has won the support of the county Planning Commission and the county government administration, which has recommended that the supervisors approve the package.

The controversy not only has pitted homeowners against developers, but has split local civic organizations, including the prestigious McLean Citizens Association, which traditionally opposes substantial deviations from the county's zoning regulations.

Tycon Developers Limited Partnership, which has constructed four smaller office buildings, including one with a doughnut-shaped arch nearby, is asking the county board to waive existing height regulations and to rezone the 11-acre site from a residential classification to high-rise commercial.

The Tycon Towers would be perched on the second highest point in the county and would stand apart as "substantially different from what is already there," said Richard D. Faubion, staff coordinator of the county's division of zoning evaluation.

The developers are courting at least two national corporations that may consider moving their headquarters into the $100-million complex, said Tycon spokesman Richard M. Patrick. The two buildings are expected to accommodate a total of about 2,500 employes, he said.

Tycon managing partner James T. Lewis said one of the developers' biggest concessions was an agreement to build a four-lane bridge from the complex over Route 7 at their own expense in response to complaints that the buildings would add to what is already one of the worst rush-hour traffic snarls in the county. Lewis said the bridge would cost the corporation $2.5 million to $3 million.

That proposal has attracted strong support for the complex from some local officials and civic organization leaders who say it could be years before the county finds the money to improve the overused roadways in the Tysons Corner area.

Richards and others argue the trade-offs aren't enough. "The real issue is that people are being beguiled into supporting the height in exchange for the ramp on land that hasn't even been rezoned," she said.

"It's the oppressive quality of a building twice as high as the Marriott that bothers us," said Richards. "In a residential area, you will feel like people are staring down at you all the time from those buildings."

Carl Zimmer, a director of the Pimmit Hills Citizens Association, says he has a greater concern: "Some homeowners feel it will have an impact on the resale of their houses. People will say, 'I like the home, but I don't want to look at that.' "

Pimmit Hills, located across the beltway from the proposed building site, is the community that would be most directly affected by the tall structures.

"The idea is not to have the buildings stick up like a sore thumb," said Lewis. He said the towers will be constructed with reflective glass that will "reflect the sky. . . to blend in with the surrounding area."

"My concern is the height precedent" the development would set, said Diane Lehman, a member of the board of directors of the McLean Citizens Association. "We've never been happy with the Tysons developments. We regard it as a gun held to our heads."