REUTERS/Francis MascarenhasBENGALURU, Sept 21 (Reuters) - Indian shares swung between small gains and losses in volatile early trading on Wednesday ahead of an expected hefty interest rate hike by the U.S. Federal Reserve to tackle inflation. Rate futures traders are pricing in an 81% chance of a 75-basis-point (bps) hike and a 19% probability of a jumbo 100 bps increase. FEDWATCHRegister now for FREE unlimited access to Reuters.com Register"We need to wait and watch the outcome of the Fed even though a 75 bps rate hike is discounted by the markets," said Anita Gandhi, director at Arihant Capital Markets. read moreThe Nifty fast-moving consumer goods index (.NIFTYFMCG) was the top gainer among major sectors, rising 1%, while the bank index (.NSEBANK) was the top drag, falling 0.6%. Among stock, shares of Central Bank of India (CBI.NS) jumped as much as 15% after the Reserve Bank of India took the state-owned commercial bank off its prompt corrective action list.

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