Miller (right) will take a newly created post as president of international, Dimon said Tuesday morning. He said she would help existing overseas operations “accelerate and prioritize their efforts and their investments for growth.”

The move comes as big U.S. banks look to faster-growing developing economies such as Brazil, Russia, India and China — the so-called BRICs — to bolster their profits.

JPMorgan Chase  has vastly expanded its reach in the United States during the financial crisis, with federally backed acquisitions of Bear Stearns and Washington Mutual. But tighter regulation and higher capital requirements are widely expected to depress profits in slow-growing, debt-soaked, rich-country markets, making overseas growth an even higher priority.

“The breadth and depth of Heidi’s international business and leadership expertise are virtually unmatched in our industry, and I’m very excited about her taking on this important new role,” Dimon said.

Miller, who placed 17^th on last year’s Fortune ranking of the most powerful women in business, has been head of the New York-based bank’s Treasury and Securities Services unit.

She has been a top aide to Dimon for years. Miller was chief financial officer of Citigroup  in the 1990s when Dimon was running the bank as No. 2 to wheeler-dealer Sandy Weill. She briefly left in 2000 to take a top job at Priceline.com , then dropped that to join Dimon at Bank One.

Dimon later engineered a merger of that Midwestern lender with JPMorgan. Since then, annual revenue at Miller’s Treasury unit has risen by half, to a recent $8.1 billion.

Michael Cavanagh, who has been the bank’s chief financial officer, will replace Miller atop Chase’s Treasury business. Doug Braunstein, who is the leader of JPMorgan’s investment banking in the Americas, will take over as financial chief.

The bank said it will name a successor to Braunstein “shortly.”