Liberal Leader Stephane Dion is promising to spend billions of dollars on bridges, roads, sewers and other capital projects if his party is elected to office.

With a possible federal election looming, Dion said a Liberal government would use any unexpected funds from a budget surplus exceeding $3 billion to create infrastructure projects across Canada.

"We will not pass onto our children crumbling bridges, leaky water pipes and insufficient public transit,'' Dion said at a speech before a conference of the Federation of Canadian Municipalities (FCM).

Dion said the Conservatives would put all of this year's estimated $10-billion surplus towards paying off Canada's debt. Dion said his party would instead put aside $7 billion for infrastructure projects, while leaving the rest to pay off the national debt.

"Imagine $7 billion to have cleaner, greener cities and communities,'' he said. "We Liberals want . . . to ensure our communities have the infrastructure that they deserve to be sustainable, healthy and competitive.''

Municipal leaders welcomed what some called a bold announcement.

"This may be one of the most significant federal policy announcements of the last decade. It is bold and it is visionary, with the potential to change the face of our country," said FCM President Gord Steeves, who is also a Winnipeg city councillor.

Berry Vrbanovic, a Kitchener, Ont., councillor and an FCM vice president, told CTV's Mike Duffy Live that investment in infrastructure helps the overall Canadian economy.

"Our big urban centres are the economic engines of this country," Vrbanovic said.

"The federal government certainly does have a role to play in terms of the economy, in terms of ensuring our communities are ready to support business in its role in the economy."

Vrbanovic said better roads and bridges help facilitate transportation of goods and help create healthy businesses and communities.

The Tories dismissed Dion's plan, saying government priorities should be debt reduction, tax relief, and some key programs.

"Canada's well-positioned in terms of fiscal policy and monetary policy to be able to weather the storm of the economic slowdown,'' Finance Minister Jim Flaherty said.

Flaherty said the Tories have already given municipalities $33 billion in a multi-year package and he has rejected pleas for more cash.

The NDP says they are not sure where the Liberals will come up with the money to pay for all of their promises.

"Where is the money going to come from," asked the NDP's national capital commission critic Paul Dewar on Mike Duffy Live.

"When you bring corporate taxes down to (15 per cent) that's tens of billions of dollars that aren't there for infrastructure. So, I have no idea how they're going to pay for this."