LEESBURG, VA (AP) Officials in one of the fastest growing counties in the country have endorsed growth controls that would block the construction of tens of thousands of homes in an area feeling the pressure of sprawl from Washington.

The Loudoun County Board of Supervisors voted 5-4 to approve the new rules, defying the expectations of landowners and developers who helped elect a Republican majority two years ago.

“I think these Republicans have forgotten that they are Republicans,” said Jack Shockey, president of pro-development group Citizens for Property Rights.

According to Census figures released July 21, Loudoun added 6,569 new homes and apartments from mid-2003 to mid-2004. The 8 percent rate of increase made it the third fastest-growing county in the United States.

The proposed development restrictions would block the construction of tens of thousands of houses worth billions of dollars in the western two-thirds of the county, a relatively undeveloped area with farms and scattered groupings of new, high-end homes about 25 miles northwest of Washington.

The proposal would allow builders to roughly double the 9,200 houses the county says are now in the area. Current rules would allow as many as 55,000 houses there. It would also provide an option to rezone property in exchange for contributions for roads, schools and other costly public projects.

A final vote probably will come near the end of the year.

“Growth is inevitable,” said Supervisor Jim Clem, a Republican who helped craft the plan. “We have an opportunity here to manage it, and you have to look at all the issues affected by it.”