The West Midlands' top transport official has renewed his call for Birmingham City Council to drop plans for an underground system.
Centro director general Rob Donald told an audience of Birmingham business representatives that a street-level system can be built in five years, whereas a vastly more expensive underground, with fewer stops, might not be completed until 2020.
The West Midlands Passenger Transport Authority, which sets Centro policy, set a deadline of July for a decision by the city council.
Mr Donald told Birmingham Forward: "The PTA said privately to Birmingham City Council in March that we needed a decision by July.
"The Black Country districts want to get on with their own Wednesbury to Brierley Hill line and they cannot wait for Birmingham forever.
"They are saying if they don't reaffirm their support by July they will go on and build the Black Country lines.
"We are not in the business of forcing transport schemes down the throats of recalcitrant authorities."
The Conservative-Lib Dem administration is against a street-level metro in the city centre because of the disruption it would cause.
It initiated a feasibility study into an underground system last year and it was due to report in May.
However, it is believed the consultants have reported back with a £2 billion scheme which would have difficulty in satisfying Government criteria for funding major infrastructure projects.
Mr Donald said: "It is much more expensive and you get less stops - one, possibly two - compared with the metro which has nine stops through the city centre.
"It will be faster but people still have to get to where they want to go when they emerge from the underground station."
If Birmingham does reaffirm its support for the metro the construction of the streetlevel scheme would halt for three Christmases to allow the busy shopping season to continue unhindered.
Birmingham Forward's chief executive Simon Murphy said the business community was looking for a swift decision from the city council.
"The results of the feasibility study into an underground option have been with the council for at least four weeks.
"If we continue to delay there is a danger that we could be overtaken in the West Midlands metropolitan area."