Montgomery County Executive Isiah Leggett has asked to meet with representatives of the two trash hauling contractors whose workers have gone on strike, in an attempt to head off any possible service interruptions for tens of thousands of residents.

County officials said the two companies, Potomac Disposal of Gaithersburg and Laurel-based Unity Disposal and Recycling, had trucks on the road Wednesday morning, some staffed by replacement workers and supervisors. While there has been no surge of complaints about service, Leggett said he wanted to meet with both management and labor to see what he could do to help resolve the disputes.

“You don’t want to wait until there have been [service interruptions] to see if there’s something you can do,” Leggett said Wednesday afternoon. “We want to make sure that the parties are working diligently to get this resolved, and not just sit on the sidelines and watch it from afar.”

Asked what leverage he might have in a private labor dispute, Leggett said he was “not sure,” but wanted to find out.

Potomac and Unity are two of the three private firms the county uses with to haul residential trash and recyclables. Together with Ecology Services of Columbia, they hold a group of 13 contracts with a combined value of $21 million to collect refuse, recycling, yard trim, bulk trash and scrap metal for more than 200,000 customers, according to the county’s Department of Environmental Protection.

Potomac and Unity have both faced allegations by workers of mistreatment and underpayment.

About 50 Potomac employees, represented by Laborers International Union of North America, struck for three days last month, charging that the company threatened immigration enforcement to gain an advantage in contract negotiations. The company said it was only trying to comply with federal immigration laws.

The talks have focused on affordable health care for company “helpers” who assist truck drivers on their routes. But they collapsed after workers rejected what Potomac called its “last best offer.” Workers said the company’s proposal would have cost helpers $65 a week in premiums — the equivalent of about a day’s pay.

In a written statement issued Wednesday, Potomac officials did not address specific proposals. It said the company “was unaware of any significant discontent of its workforce” until Laborers International filed a petition for a union election at the firm last year. It accused the union of filing multiple unfair labor practice charges with the National Labor Relations Board (NLRB) in an effort “to drive up the Company’s legal fees and distract the Company from its obligations to the County.”

Potomac also said that even though employees voted to reject unionization last year, the company had no choice but to recognize Laborers because of the “incessant” federal complaints.

Brian Petruska, an attorney for the union, acknowledged that the union lost the election by one vote. But he said the company actually agreed to recognize the workers as a bargaining unit to head off federal charges that it was impossible to have a fair election at Potomac because of intimidation and other management practices.

A complaint by the NLRB issued in February said the company’s conduct was “so serous and substantial in character that the possibility...of conducting a fair rerun election by use of traditional remedies is slight.”

Workers at Unity said they reached out to the union after reading and hearing about the strike at Potomac. They said they were in the process of organizing an election when a worker was fired Monday for speaking out in a compulsory meeting called by the company.

About forty workers were standing outside the company gates Wednesday morning when the company delivered a letter in Spanish telling them they had been fired. London Bryson, the company’s human resources director, declined to discuss the termination or the status of the workers, except to say that they represented a small fraction of the company’s workforce.

Union officials said that while only 40 or so workers stayed out off the job, many more have signed cards favoring the union.