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BENGALURU, May 31 (Reuters) - Indian shares fell on Wednesday, snapping a four-day winning streak, dragged by index heavyweight Reliance Industries and financial stocks, ahead of gross domestic product data for the March quarter due later in the day.

The blue-chip Nifty 50 index lost 0.53% to 18,534.40, while the benchmark S&P BSE Sensex closed 0.55% lower at 62,622.24.

Both indexes had hit new five-month highs for three sessions in a row and were in overbought territory before Wednesday's slide.

Reliance Industries Ltd, India's largest firm by market capitalisation with a 10.32% weightage in Nifty 50, lost 2%.

The oil-to-telecom conglomerate could see $155 million in outflows, following a decrease in its MSCI weightage, according to Nuvama Research. The MSCI index rejig comes into effect post market close on Wednesday.

Six of the 13 major sectoral indexes logged losses, with the high-weightage financials falling 0.82%. India's largest state-owned lender, State Bank of India Ltd, lost 2.18% on its record date for dividend.

Investors awaited a vote on the U.S. debt ceiling agreement deal, due on Wednesday. "Its outcome would determine the market direction in the near to medium term," said Shrikant Chouhan, head of equity research (retail) at Kotak Securities.

While the deal is expected to pass, uncertainty prevailed about whether the U.S. Congress will approve the deal after some Republican lawmakers vowed to stall it.

Investors also await India's gross domestic product (GDP) data for the quarter ending March 31. A Reuters poll of economists estimated the economy grew by 5%, accelerating from 4.5% in the previous quarter, aided by steady urban demand and government spending.

Bucking the trend was pharma, which gained 0.6%, led by a rise in Sun Pharmaceutical Industries Ltd on Chinese nod for plaque psoriasis drug and Torrent Pharmaceuticals Ltd on strong March quarter earnings.

($1 = 82.7159 Indian rupees) (Reporting by Bharath Rajeswaran in Bengaluru; Editing by Nivedita Bhattacharjee, Dhanya Ann Thoppil, and Janane Venkatraman)