U.S. Chamber of Commerce President and CEO Tom Donohue said Thursday a chamber legal challenge is “a possibility” when the Department of Labor’s proposed fiduciary rule for retirement plan advisors is finalized.

Donohue attacked the rule as flawed during his annual State of American Business address, claiming it could limit small businesses’ access to retirement services or lock them out of the retirement market altogether.

However, he acknowledged he hasn’t read the proposal.

Looking ahead to the new year, Donohue said the chamber will be aggressive in working for entitlement reform, labeling it as an absolute priority.

Without fixes, he said, Social Security and Medicare won’t be able to pay full benefits in 20 years.

“If we make common-sense changes soon, we can ensure the nation’s safety net remains intact for future generations,” said Donohue.

The chamber chief called the current recovery the worst since the Great Depression, noting 10 percent of workers are either out of a job or underemployed while the workforce participation rate of adults is at a four-decade low.