Lefty Gen-Z City Councilman Chi Osse is preparing to challenge Democratic House Minority Leader Hakeem Jeffries in the US House next year — against the explicit objections of mayor-elect Zohran Mamdani, The Post has learned.

“He said he wants to strike when the iron is hot,” one insider said of the TikTok pol.

The source said that Mamdani had told Osse that he didn’t want him to challenge Jeffries in the primary, believing it would disrupt the fragile peace between the far-left of the party and moderates.

Mamdani worked for months to woo the establishment of the party to unite ahead of his mayoralship.

“Strike while the iron is hot?” another insider complained, adding, “How about listen to the next mayor, who is the hottest thing in politics right

The second source confirmed Osse has already started hiring his staff to challenge the Brooklyn Democrat.

The falling-out between Osse and Mamdani — two social-media-savvy pols — even kept Osse from attending the victory party follow the mayor-elect’s historic win last Tuesday night.

Osse became a card-carrying member of the Democratic Socialists of America (DSA) again over the summer after leaving in 2020.

The feud highlights what insiders have opined will be a real problem for the 34-year-old mayor-elect as he tries to enact his lofty socialist policies.

Insiders say Mamdani needs to keep the peace between the party establishment, including Gov. Kathy Hochul, and the insurgent far-left — which is trying to capitalize on his win and challenge more moderate.