MetLife Inc. Chief Executive Officer Steve Kandarian has seen regulation hinder his company’s capital plans since he took over the top job at the largest U.S. life insurer in 2011.

The Federal Reserve limited New York-based MetLife from returning capital to investors when it was a bank-holding company. After selling deposits to rid itself of that distinction last year, MetLife has avoided stock buybacks because it can’t be certain whether the Fed will label it a systemically important firm, and what rules might be imposed, Kandarian wrote today in a letter to shareholders.

“It is taking much longer for clarity on the capital rules than anyone had anticipated,” Kandarian wrote. “A number of our shareholders are frustrated with our cautious approach to returning cash during this period of regulatory uncertainty. We share your frustration.”

MetLife is in the final stage of consideration to be designated a systemically important financial institution, which could lead to stricter capital, leverage and liquidity requirements from the Fed. Kandarian has said his company doesn’t pose a threat to the financial system. If MetLife is deemed systemically important, the company has said the Fed should impose rules designed for insurers, rather than banks.

“If federal capital rules for life insurers do not appropriately reflect the business model of insurance, we could be forced to raise prices to consumers or exit markets entirely,” Kandarian wrote. “Regulators in Washington must recognize that imposing higher capital requirements on certain life insurance companies is not cost-free.”

MetLife raised its quarterly dividend by 49 percent in April, the first increase since 2007. It last authorized a buyback in 2008. MetLife has rallied 39 percent in the past year, trailing the 48 percent gain of smaller rival Prudential Financial Inc., which is based in Newark, New Jersey.

Prudential and American International Group Inc. have already been designated systemically important. Prudential had $500 million remaining as of Dec. 31 under a $1 billion share repurchase program authorized in June.

–With assistance from Ian Katz in Washington.