U.S. public pension funds are expected to report poor annual returns in the coming weeks, results that are likely to increase calls for more realistic retirement promises for teachers, police officers and other public workers.

At least three of the nation's largest U.S. public pension funds have already announced returns of between 1 percent and 1.8 percent, far below the 8 percent that large funds have typically targeted.

The fund's targets have been "unrealistic," said Michael Lewitt, a portfolio manager at Cumberland Advisors in Sarasota, Florida. "They've been fooling themselves because there is no realistic case they can make that."

The euro zone debt crisis, record low interest rates and weak growth across the globe made the last year a meager one for financial investments in general. U.S. public pension funds were no exception.

"Failing to understand the scope of the pension crisis sets taxpayers up for a bigger catastrophe in the future," said Bob Williams, president of free-market think-tank State Budget Solutions, in Washington.

"Without government action, states, counties, cities and towns all over America will go bankrupt," he said.