And the NDP leader says that commitment must be made in the next budget in 2013 since the current Building Canada Fund is set to expire the following year.
The fund, launched in 2007, has pumped some $33 billion into municipal infrastructure projects.
The Federation of Canadian Municipalities is calling for a new 20-year plan, which would include increasing current federal spending on infrastructure by $2.5 billion annually.
The federation also wants municipalities to be able to spend federal money as they see fit, rather than having to apply for funding for each project.
Mulcair supports the federation's recommendations in principle but is not committing to a specific dollar amount, other than to promise that an NDP government would turn over another one cent per litre of the existing gas tax to municipalities.
"Beyond that, we're not making any undertaking with regard to that ask," Mulcair said following a speech Thursday to the federation.
The amount of funding will depend on the state of the economy and the state of the books at the time of the next election in 2015, he added, noting that the Conservatives have pushed back their target for eliminating the deficit by a year to 2016-17.
"What we are talking about is the priority that the NDP would give to long-term, sustainable funding, predictable funding, partnering with the provinces and therefore with the municipalities, to make sure that we no longer have this crumbling infrastructure without the ability to take care of it," Mulcair said.
"That's the undertaking we can make realistically."
Mulcair ruled out one of the federation's proposals, to allow municipalities to levy a one cent value-added tax or "penny tax."