Prime Minister Stephen Harper is scheduled to unveil long-awaited details of a new 10-year infrastructure fund, which Ottawa wants to use to boost private investment in infrastructure and apprenticeships.

The Building Canada Fund was announced last year in the 2013 budget, but municipalities have been left in the dark in terms of how to apply for the money. Mayors have been increasingly vocal of late, warning that the delays in Ottawa risk postponing important long-term infrastructure projects.

Mr. Harper and federal Infrastructure Minister Denis Lebel are scheduled to release those details Thursday afternoon at a museum and community centre in Gormley, Ont.

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The 2013 budget said the fund would be worth $14-billion over 10 years and would support major economic projects of national, regional and local significance. It would be in addition to a $32.2-billion, 10-year Community Improvement Fund for community infrastructure and $1.25-billion for the P3 Canada Fund, which is focused on public private partnerships in infrastructure.

The 2013 budget said the Building Canada Fund would also have a "P3 screen," meaning applicants will have to see whether a project would be a good fit for a public private partnership.

The budget also said provinces, territories and municipalities that receive funding will be encouraged to use apprentices. The 2014 budget expanded Ottawa's focus on encouraging apprenticeships and training for jobs in the skilled trades.

In September, Mr. Harper and Finance Minister Jim Flaherty held an event with Toronto Mayor Rob Ford to announce a $660-million subway extension to Scarborough. The federal government said the money would come from the new Building Canada Fund, but other big-city mayors wondered how Toronto secured money from a program that had not yet been launched.

Calgary Mayor Naheed Nenshi expressed concern on Tuesday, the day of the budget, that there were still no details.

Mr. Nenshi said municipalities were promised they would get the criteria and details about how to apply for the fund so no one would miss a construction season. "It's really, really important that the federal government announce the criteria now," he said. "For many municipalities, it may in fact be too late."

Mr. Flaherty rejected suggestions that the upcoming construction season is at risk, noting that several billion dollars remain in another infrastructure fund that is about to expire.

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"The current program is just expiring; the new program is just commencing," he said. "So I don't know why anyone would have expected to get money under the new program before it even starts."

With a report from Kelly Cryderman in Calgary