OTTAWA -- Cities and provinces with new, shovel-ready infrastructure projects will be eligible for funding under the first phase of the Liberal infrastructure program, but only if the work is completed within the next three years.

That's the message in letters which federal Infrastructure Minister Amarjeet Sohi sent to his provincial counterparts last week.

Project costs for transit and waste-water and water-treatment projects will be eligible retroactive to April 1, "so work can begin immediately," Sohi wrote.

The first phase of the Liberals' promised 10-year infrastructure plan wraps up in 2019 -- just as the country heads to the polls in a federal election -- and is mostly focused on repairing aging roads, pipes and transit systems across the country. It is also designed to lay the foundation for the second and more lucrative phase of the Liberal plan by covering planning costs for larger projects.

"There is money for design, there is money for planning and there is money for doing small projects if they are ready to move ahead with them," Sohi told reporters at the Liberal cabinet retreat in Kananaskis, Alta.

"There are big challenges related to not doing the rehabilitation and the repairs that are necessary and for Phase 2 we have already started consultations with (cities) and that's where we will have the opportunities to support transformative projects."

The Federation of Canadian Municipalities says there are many projects that could be eligible, from transit stations in Vancouver to waste-water treatment systems in Victoria and St. John's that are among 106 systems that need upgrades in the next four years at an estimated cost of $3.5 billion.

Money can't go to municipal projects without funding agreements between the federal and provincial governments.

"What these letters today do is that they set the framework and gives clarity for provinces and territories from the federal government for those negotiations and discussions to occur," said FCM president Raymond Louie.

The Liberals pledged in the budget, flowing from a campaign promise, to double infrastructure spending over the next 10 years to bring the overall federal investment to $120 billion. The first two years of the new infrastructure program has $6.6 billion for provinces and cities, not including money promised to First Nations infrastructure or to universities.

The Liberals also promised changes to the government's existing marquee infrastructure program, known as the New Building Canada Fund, to quickly move about $8.7 billion remaining from the provincial and territorial stream of that fund to cities and provinces. The Liberals want the remaining money allocated to projects within the next two years.

The government is expanding eligibility under the fund, including work on small-scale highways and roads in provinces like Prince Edward Island that previously didn't qualify because they weren't big enough in scope or impact.

The federal government is also going to fund eligible project costs for ferry systems that provinces like B.C. wanted included in the fund.

NDP infrastructure critic Matthew Dube said problems with the design of the fund could still cause problems for cities and provinces, even though the government relaxed eligibility criteria.

"Does that mean the stated goals would actually be accomplished? I don't think so," Dube said.

"We really needed to build a new infrastructure program from the ground up that would actually take into account what the provinces and territories and municipalities and all the communities involved have said are the problems."

Sohi's letters also show the government will cover up to half the cost of disaster-mitigation projects, including those that would fight floods in provinces like Alberta and Manitoba, and any projects delivered as a public-private partnership, known as a P3.

The government has removed the requirement for communities to always look for a private-sector partner on projects, but hasn't abandoned the idea: In a speech last week at a conference on public-private partnerships, Sohi said the government believes some projects are best suited to a P3, citing the new Champlain Bridge in Montreal and the Gordie Howe International Bridge in Windsor, Ont.

-- With files from Joan Bryden