TORONTO - Ontario will be in the red for a few years as it limps through a recession, starting with a "significant" deficit in the upcoming spring budget, Premier Dalton McGuinty warned Monday.

Some predict Ontario's deficit will reach at least $5 billion this year, taking into account a $500-million shortfall the government forecast in the fall, as well as the billions of dollars that have since been promised for infrastructure and troubled automakers.

McGuinty wouldn't confirm the $5-billion figure, but suggested it wasn't too far off.

"Some of the numbers are already out there and people can make those calculations, I think, pretty accurately on their understanding of how things are unfolding," he told The Canadian Press.

"I think that we're going to run a significant deficit. I'm not going to put a number on it, but we're going to do it for the right reasons."

McGuinty has changed his usually cheery tone about Ontario's economic situation in recent days, painting a far gloomier picture of what's in store during a series of rare sit-down interviews with reporters.

The premier said he only wants to prepare Ontario residents for what's ahead, but critics have already interpreted his rhetorical shift as laying the groundwork for cuts to services like health care and schools.

McGuinty wouldn't say whether cuts are on their way, but predicted the province will pay a price for running "multi-year" deficits.

Spending will slow, and Ontarians will have to "temper" their demands on how much more can be invested in provincial programs, he said.

"Let's not be carried away with deficit euphoria," he said.

"We will not be able through our budget to do everything we would like to do."

McGuinty also acknowledged that his five-point economic plan may not be enough to get Ontario back on track and more "fundamental changes" will be required.

"We're going to have to do more to enhance our competitiveness if we are going to achieve the rates of growth we need to support the quality of public services that we have come to expect, and to support the standard of living that we'd like to hand down to our kids," he said.

"What I've learned is that we're going to have drill deeper here now, beyond the five-point plan, beyond the support for public services."

The premier says the economy won't come back as strong unless fundamental changes are made, such as increasing business investment and having more workers with post-secondary education.

The governing Liberals forecast a $500-million deficit in their fall economic update, but have recently hinted that the figure may turn out to be much larger.

McGuinty has committed to matching federal dollars for infrastructure projects in the province and providing $1.3 billion to bail out troubled automakers.