Citigroup President Jamie Forese, likely the banking giant’s next chief executive, is merging its investment banking and underwriting operations under his supervision.

The change, announced in an internal memo obtained by The Post, is the second major reorganization at the bank this week, after CEO Michael Corbat disclosed internally the retirement of CFO John Gerspach and the promotion of other executives.

The move, which merges two businesses already under Forese, essentially combines two different operations that usually work hand in hand on Wall Street — raising money and investment banking.

The reorganization was done “with a view toward serving our banking clients with a more comprehensive coverage model, aligning our capital raising and advisory products more seamlessly,” Forese said in the memo Thursday.

It was done as the bank is reallocating funds and choosing who’s up for promotions — signaling a new direction for the bank.

“You kind of want the new people to put their stamp on it now vs. inheriting at the beginning of the year working under someone else’s plan,” one bank executive told The Post.

The new, merged divisions, called Banking Capital Markets and Advisory, will be chaired by Ray McGuire. Long-time bankers Tyler Dickson and Manolo Falco will be the global co-heads, according to the memo.