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By Mark Felsenthal

WASHINGTON, June 12 (Reuters) - New U.S. accounting rule changes governing financial firms' off-balance-sheet vehicles won't change the results of recent government tests of the biggest U.S. banks' capital levels, the Federal Reserve said on Friday.

However, the Fed said it is reviewing capital standards in light of the changes.

The Financial Accounting Standards Board issued new standards that will affect the way banks account for off-balance-sheet vehicles and provide information about them.

The new rules could force banks to move more assets onto their books and could affect trillions of dollars of assets when they take effect in 2010.

The rules raised some worry among regulators and bankers that they might move tainted securities back onto bank balance sheets precisely at a time when the government is trying to restore bank health after the financial meltdown that began in August 2007.

To build confidence in banks, the Fed tested how 19 of the largest institutions would fare if unemployment rose higher, the economy slowed further, and house prices slumped even more. Ten of the 19 banks tested needed to raise a total of $74.6 billion in capital to hold adequate capital buffers, the exercise disclosed.

But the so-called stress test was greeted with relief and banks have raised billions in private capital since it was administered.