Citigroup (NYSE:C) and Apollo Global Management (NYSE:APO) are joining forces to form a landmark $25B private credit, direct lending program initially in North America, the Wall Street heavyweights said Thursday.

Citigroup and Apollo Global Management are teaming up in the fast-growing private credit market, agreeing to work together on $25 billion worth of deals over the next five years. The two Wall Street heavyweights have struck an exclusive partnership to arrange financings for corporate and private equity clients,

Zelter joined Apollo in 2006 after more than a decade at Citigroup, where he had once served as the chief investment officer of a division that invested in private assets. Before that, he oversaw the bank’s global high-yield and leveraged finance business. Citigroup is a frequent underwriter of debt deals for Apollo’s private equity business.

Citigroup and Apollo Global Management have agreed to a $25 billion private credit and direct lending program, starting in North America and potentially expanding. This aims to enhance access and funding certainty for strategic transactions,

Citigroup Inc. C and Apollo Global Management Inc. APO have inked a deal for a subsidiary of Citigroup and certain affiliates of Apollo to establish a revolutionary $25-billion private credit, direct lending program.

Citigroup Inc. and Apollo Global Management Inc.’s “impossible to replicate relationship” is what brought the landmark private credit partnership to fruition, said Richard Zogheb, the bank’s global head of debt capital markets.