The county in 2007 granted Pfizer $6.7 million of abatement on half of its property taxes to help finance a $50 million biologics research building at its Chesterfield campus. The pharmaceutical company then agreed to maintain 1,035 jobs on the campus.

Officials have not calculated the amount of the added taxes because the company did not keep the agreement. The total would depend on the number of employees on Sept. 30, the closing of Pfizer's sale of its campus to Monsanto Co. and reassessments starting in 2011, officials of the county economic council said Monday.

County Executive Charlie A. Dooley last Friday asked the County Council to adjust documents relating to the tax abatement to take the penalty and Pfizer's sale into account.

If the County Council agrees, Monsanto would pay the unabated taxes and Pfizer would pay additional taxes as a penalty for each year the job total did not meet its target. New Monsanto employees at the campus would be part of the 1,035 jobs target.

Monsanto and Pfizer could pay as much as 80 percent of taxes levied against the property, officials said.

Ed Bryant, a spokesman for Pfizer, said he did not know how many workers the company actually has laid off. The number, he said "is a moving target." The company, he said, is reducing workers by closing work groups here.

Dennis Coleman, president and chief executive of the economic council, declared: "These talented employees are an asset. We are doing what we can to keep them here."

Before the layoffs, Pfizer had done more than promised to develop the Chesterfield campus, Coleman said.

The state has given Pfizer $2 million to retain 1,000 workers. John Fougere, spokesman for the Department of Economic Development, said the state has not decided what it would do about imposing a penalty because of the layoffs.