Premier Dalton McGuinty says it's too early to talk about a new tax to pay for transit improvements in the Greater Toronto Area.

Mississauga Mayor Hazel McCallion says she wants the province to consider a new tax to pay for $50 billion in transit upgrades over 25 years to deal with gridlock.

McGuinty says he welcomes McCallion's enthusiam for tackling the issue of gridlock, but he wants to wait for MetroLinx to recommend ways to foot the bill.

The provincial transportation agency is expected to issue its recommendations on how to fund the public transit projects a year from now.

McGuinty says he first wants people to engage in the debate about gricklock and what will happen if nothing is done to address the problem.

The premier spoke to high school students on Friday in Waterloo, where he said he has until October to call a byelection to replace Tory Elizabeth Witmer.

McGuinty refused to rule out a summer byelection, but said he wants to give all the parties time to find a candidate.