The head of transport in Greater Manchester has reacted cautiously to suggestions the area could trial "pay-as-you-go" road charge plans.
Greater Manchester could trial the government's scheme
Councillor Roger Jones said he wants positive news about plans to expand the Metrolink tram network first.
Transport Secretary Alistair Darling says the anti-congestion charges would replace road and fuel tax.
He said a light rail system was needed before measures aimed at getting people onto public transport were viable.
Mr Jones, who is chairman of Greater Manchester Passenger Transport Authority (GMPTA), added: "We've been spending a long, long time now convincing civil servants at the Department of Transport that Metrolink is the answer for Greater Manchester.
"There were some civil servants who felt you could do everything that the tram could do by bus and we've convinced them now that that would be absolutely impossible."
Mr Darling's plan would see cars fitted with devices which could be tracked by a satellite to show where they had been.
Driving in rural areas could cost as little as 2p a mile while using busy roads during rush hour could cost up to £1.34 a mile.
The scheme would replace fuel and road tax.
Mr Jones said he believed Greater Manchester or the West Midlands would trial the scheme.
Plans on hold
He added: "Those two are the biggest conurbations and I think it's more than likely they'll be going to Manchester or Birmingham."
The proposed expansion of Metrolink across the conurbation was put on hold when Mr Darling said in December 2004 that the government could not afford the estimated £900m cost.
Prime Minister Tony Blair has since reiterated his support for the scheme, but the government has only offered £520m with GMPTA expected to find a way of funding the rest of the project.
If it is approved the network would be extended with lines to Oldham and Rochdale, Ashton and south Manchester.