Representatives of private Iranian construction companies accompanying Zarif on a visit to Nicaragua's capital discussed the possibility of getting a slice of the $50 billion project, the minister told a news conference.
The ambitious plan calls for a waterway linking the Pacific and Atlantic oceans that would rival the century-old one in Panama, which has recently been expanded to take bigger ships.
Yet work on Nicaragua's canal, meant to have started two years ago, has not begun. HKND, the Chinese group tasked with the huge job, now says it should start at the end of this year.
Iran has enjoyed good relations with Nicaragua, one of the poorest states in the Americas, and particularly its leftwing president, former rebel Daniel Ortega, who returned to power in 2007.
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Both countries share an antipathy towards the United States.
Zarif made Nicaragua the second stop of a Latin American tour that began Monday in Cuba and which was to include Ecuador, Venezuela, Bolivia and Chile.
Nicaragua's government spokeswoman and First Lady, Rosario Murillo, said officials discussed investment opportunities with the Iranian delegation in the canal and other areas.
Ortega is running for re-election in November and has named his wife as future vice-president if he wins.
His victory looks likely after courts in recent months ordered opposition lawmakers and a party chief be replaced with figures hewing to Ortega's positions.