Only one member of the committee, Thomas Hoenig, voted against holding rates steady because he "believed that continuing to express the expectation of exceptionally low levels of the federal funds rate for an extended period was no longer warranted because it could lead to a build-up of future imbalances and increase risks to longer run macroeconomic and financial stability, while limiting the committee's flexibility to begin raising rates modestly."
The Fed has said there's no specific definition for "extended period" and it could take action anytime it's needed.
The Fed has yet to address a $2.3 trillion balance sheet that includes $1.25 trillion in mortgage-backed securities acquired March 31 to keep home loan rates low. The Fed could gradually sell of the assets to avoid the risk of rising interest rates, on Fed official has suggested.
With financial markets continuing to improve, the Fed also announced the closing of all but one of its special liquidity programs created during the 2008 financial crisis. The Term Asset-Back Securities Loan Facility, the only remaining program, is scheduled to close June 30 for loans backed by new-issue commercial mortgage-backed securities. It closed March 31 for loans backed by other types of collateral.