The federal labour minister has told the Amalgamated Transit Union to vote on the city's contract offer by Jan. 9 at the latest.

Rona Ambrose and her department were unable to broker a deal between striking transit workers and the City of Ottawa after the latter asked her to intervene last week and force a vote that would end the three-week walkout.

"I am of the view that it is in the public interest, at this time, to direct a vote," Ambrose said in a statement released late-Wednesday afternoon, adding she still hoped for a negotiated settlement.

"I am concerned about the impacts that this work stoppage is having on the traveling public who have no other readily available mode of transport, particularly the elderly and people who are dependent on this service.

"Therefore I have decided to provide an opportunity to the employees in the bargaining unit to accept or reject the last offer received from the employer."

Ambrose made the decision under section 108.1 of the Canada Labour Code, designating the Canada Industrial Relations Board to conduct the vote as soon as possible.

Ambrose has also asked the CIRB to review OC Transpo's potential status as an essential service, citing concerns about public health and safety. The board is an independent tribunal that interprets and applies federal law regarding bargaining rights and unfair labour practices.

Special council meeting set for Jan. 5

The federal government's decision to hold a supervised vote confirmed what senior Conservative sources had been saying since Monday -- that Ambrose would overrule the union executive if there was no vote. The ATU had urged Ambrose to reject the city's request.

City Hall sources have told CTV Ottawa that Mayor Larry O'Brien will call a special council meeting on Jan 5.

About 2,300 OC Transpo drivers, dispatchers and mechanics walked off the job Dec. 10 after working without a contract since April.

Even if the strike is settled soon, all buses will stay parked for five to six days while mechanics service the vehicles.

Negotiations between the two sides broke off Christmas Eve after the city made an offer the previous day.

The main sticking point of the dispute remains control over bus driver scheduling, which OC Transpo management wants to take back from drivers.