Montgomery County Executive Charles W. Gilchrist yesterday rebuked Prince George's County Executive Parris N. Glendening for filing suit against a bicounty transit commission and said the legal action threatens the future of Montgomery's ride-on bus service.

In a "Dear Parris" letter to Glendening's office yesterday, Gilchrist complained that a recent Prince George's suit against the Washington Suburban Transit District "ignores your previous agreements, attempts to rewrite legislative history, reneges on a bicounty understanding and jeopardizes our counties' good working relationship."

Gilchrist's letter was the latest salvo in a longstanding war of words the two counties have waged over state funding for payments to Metro. Those funds, administered by the transit district's six commissioners, were delayed this summer when officials could not agree how to divide the money between the counties.

In a suit filed Aug. 16 in circuit court, Prince George's officials alleged that the transit commissioners unlawfully withheld $5.5 million that should have been paid to Metro on July 1.

The suit asked that the transit district be ordered to release the money, which Montgomery and Prince George's have had to offset with their own funds.

In previous years, Montgomery has received credit for proportionately more money as a "rebate" for operating its ride-on bus service. In his letter, Gilchrist said that the Prince George's suit threatens that annual $540,000 compensation for the ride-on program.

Gilchrist warned Glendening that by suing the transit district, Prince George's could lose Montgomery's support in next year's budget battles in the General Assembly.

Glendening could not be reached for comment. John Wesley White, his chief administrative officer, said officials were "surprised by the tone and substance" of the letter. "We don't accept responsibility to pay for the ride-on program out of our fair share of state aid," White said. "That's $500,000 of our money that previous executives had given away."

White said Prince George's will not drop its suit but is willing to negotiate with Gilchrist over distribution of transit funds.