Road pricing in Wales would only be applied to new major road projects, according to the deputy first minister.
Road charging would not be applied to existing roads
Ieuan Wyn Jones told BBC Wales' Politics Show, if a charging scheme for motorists was brought in, it would not be applied to the current road network.
Ministers will soon have the power to introduce schemes in Wales, under clauses in the new local transport bill.
No decision on how to use the new power has yet to be taken.
Mr Jones, who is minister for the economy and transport, said: "There's no prospect whatsoever of introducing charges on the existing network."
But he said it would be considered on future big infrastructure projects where there were congestion issues.
"That's the only kind of scheme in which it would be practical," added Mr Jones.
There has already been speculation that future charging may involve the planned M4 relief road near Newport, which could open between Magor to Castleton by 2013, if a business case goes forward.
Mr Jones said local authorities could also be given provision for applying for congestion charging.
Three years ago, a document prepared for the cabinet said road chargng had a key role to play in the assembly government's future transport plans.
Road tolls are seen as a potential way of reducing congestion, although environmental groups have urged ministers to move the emphasis from roads to public transport, cycling and walking.
Mr Jones told a transport conference last week that one of his first aims for transport spending was a "swift north-south rail service that met business needs and cut down on many car journeys."
The assembly government's new transport strategy is expected to be published in the spring.