Transport secretary Michael Matheson said he was confident most people would comply with the “expectation” that they wore a covering.
Passengers are also expected to bring their own coverings, but Caledonian Sleeper has started providing them and ScotRail is considering it.
New Scottish Government guidance said operators “may wish to have their own stocks available as an initial encouragement to those passengers without face coverings”.
But First Bus, one of Scotland’s biggest operators, said free masks could pose a risk if they were discarded by passengers.
Mr Matheson said: “I am very aware of the public sentiment around having a face covering on public transport.
“That was one of the factors taken into account in the decision to ask people to have a face covering.
“We have gone from a position where people could use one if they wished to saying we now expect you to have a face covering if you are on public transport, in recognition of other travellers and of transport workers.
“The travelling public in Scotland will recognise that having a face covering is the right thing. I’m sure the majority will comply with that.
“I’m presently not looking at compulsory face coverings.
“Enforceability would present challenges.”
Mr Matheson said they included drivers being the only member of staff on board most buses.
A Scottish Government spokesperson added: “We don’t want to make it mandatory because we trust the good sense of the people of Scotland.
“But should, in the light of experience, circumstances dictate, then we will, reluctantly, have to seek powers by means of legislation in the Scottish Parliament.”
Mr Matheson admitted passengers were likely to come closer than 2m, such as when boarding and alighting.
However, there were no plans to reduce physical distancing to 1.5m or 1m, as in some other countries.
He said: “By the physical nature of public transport, it is likely the 2m distancing is going to be compromised, and that is why the public should look at alternatives, where that is appropriate.
“The important thing the public health guidance says is you minimise the time frame in which that may occur - so try to make sure it happens for as short a time as possible.”
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