* Fed pushes back hard against political pressure

* Kohn: eroding Fed independence risks U.S. AAA rating

* Kohn says investors may worry Fed monetizing U.S. debt

By Alister Bull

WASHINGTON, July 9 (Reuters) - The U.S. Federal Reserve on Thursday launched a robust defense of its independence and warned that efforts in Congress to put monetary policy under political sway would hurt the economy.

Fed Vice Chairman Donald Kohn said opening up some of the U.S. central bank's most sensitive decisions to political scrutiny could result in higher long-term interest rates and hurt the United States' credit rating.

Testifying before a congressional panel, Kohn sought to beat back a proposed bill that would open the U.S. central bank's policy decisions to audits by a federal watchdog agency. More than half of the members of the U.S. House of Representatives have signed as co-sponsors of the measure.

"Any substantial erosion of the Federal Reserve's monetary independence likely would lead to higher long-term interest rates as investors begin to fear future inflation," Kohn told a House subcommittee.

Kohn's testimony comes as Congress debates President Barack Obama's plan for regulatory reform, which envisions the Fed taking on an expanded role monitoring risks across the entire financial system to help ward off future financial crises.