Melbourne's public transport system is on the brink of being paralysed by strikes, with Yarra Trams staff voting to join rail workers in taking industrial action.

The move means train and tram drivers could strike at the same time, with Rail, Tram and Bus Union (RTBU) members on Tuesday endorsing tram stoppages of up to 24 hours.

The union's tram division secretary, Phil Altieri, said simultaneous industrial action was a possibility.

"We are not ruling anything out at this stage," he said.

"We don't want to be in this position, but having said that, we will do what it takes to get our members a fair and reasonable deal."

The union has rejected Yarra Trams' pay offer of 9 per cent over three years, which is half the amount staff have been pushing for since April.

More than 99 per cent of RTBU members voted for an industrial campaign that included tram stoppages, refusing to short shunt trams and overtime bans.

But Mr Altieri said strike action would be a last resort.

"Our members have made a substantial contribution to the company's success and expect to be rewarded accordingly," he said.

Yarra Trams spokesman Simon Murphy said its offer was fair.

"Yarra Trams remains committed to reaching a fair and balanced agreement and keeping trams moving," he said.

At the same time, a day of urgent talks between the union and Metro Trains aimed at averting a railway strike next week did not result in a deal.

Metro staff have threatened to strike for four hours next week and give commuters two "free travel days", where station barriers would stay open and inspectors would refuse to check myki cards or issue fines.

Public Transport Minister Jacinta Allan said the talks, which came at the request of the Victorian Government, were still "productive".

"We reiterate that it is in no one's interest for action to be taken that has the potential to affect thousands of Victorians," she said.

"The Government will continue to work closely with all sides to see these issues resolved as quickly as possible."

Looming train strike the first in almost two decades

The union insisted the industrial action was aimed at Metro's hip pocket, not the public.

Opposition spokesman David Hodgett said the Government should pressure the parties to reach a deal.

"They should be saying, 'you're not leaving until this is resolved. Our transport system is essential to the state, we don't want to see strike action'," he said.

It would be the first time in almost 20 years that Melbourne's trains have ground to a halt because of an industrial dispute.

The protected action covers train drivers, station officers, ticket inspectors, signallers, controllers and administration staff.

The union has demanded an 18 per cent pay rise over three years as part of negotiations for a new wage deal with Metro.

RTBU executives will meet on Wednesday to discuss the industrial action for Metro and Yarra Trams staff.