Citigroup Inc., the third-biggest U.S. bank, may exit or pull back from businesses in 21 countries that are among its least-efficient markets as Chief Executive Officer Michael Corbat seeks to cut costs.

The countries produce less than 10 percent of New York-based Citigroup’s revenue and have a “very low” return on assets of 0.4 percent, Corbat, 52, said in a presentation.

“These results are unsustainable,” Corbat said. “In these markets, if there is not a clear path to acceptable returns, we intend to significantly scale back or exit certain business lines.”