The Loudoun County Board of Supervisors narrowly kept alive last night a crucial element of its land-planning program, an ordinance that would encourage construction of new villages.

On a 4 to 3 vote, the board set up a showdown for Feb. 19 on the measure, which has heated emotions in the growing county of 90,000. The village proposal is part of the board's "vision" initiative for guiding development in Loudoun.

Nearly three years in the making, the village ordinance is designed as a voluntary option for development of rural land that would limit suburban sprawl. It would allow developers to cluster homes and stores in a town center, surrounded by permanent open space that could encompass 80 percent of the total acreage of a new village. Up to 300 homes would be permitted.

Preservationists, many from rural western Loudoun, have supported the concept, saying the design is preferable to dotting hillsides with evenly spaced houses. However, many say that proposed density bonuses and community sewage treatment plants would encourage far more overall construction than current laws allow.

Meanwhile, some developers have said the plan would not give them enough incentive to spend the additional time and money needed to gain approval of a village plan. Some supervisors said last night they will vote against the ordinance in two weeks.

Supporters said it is time to dispose of the issue, shunning a proposal to set up a study committee that would delay action at least three months. "I don't want {the ordinance} just hanging out there in never-never land," said board Vice Chairman Charles A. Bos (D-Leesburg).

With a massive budget deficit and election-year politics expected to dominate public debate this year, some officials and others say it may be difficult to pass the village ordinance if it is significantly delayed.

A similar ordinance, limited to so-called hamlets of up to 80 homes, was enacted last year by the supervisors. Although most Loudoun residents live in the suburban, eastern part of the county, the vision program for that region has not proceeded in the three years since the current board took office.

Top Loudoun officials conceded yesterday that they are disappointed with the progress of the vision initiative. The entire board faces election in November.