March 20 (Reuters) - Shares of U.S. lender First Republic tumbled nearly 50% on Monday on fears it will need a second rescue to stay afloat, bucking a broader rally in bank shares driven by UBS Group's state-backed takeover of Credit Suisse. "First and foremost, the Credit Suisse, UBS merger certainly takes a lot of stress out of the global banking system." The 3 billion Swiss franc ($3.2 billion) deal for the troubled Swiss bank - which was once worth more than $90 billion - was engineered by Swiss regulators and announced on Sunday. European bank shares (.SX7P) rebounded from recent losses, while on Wall Street the S&P 500 banks (.SPXBK) index recovered 0.6%. [1/2] Buildings of Swiss banks UBS and Credit Suisse are seen on the Paradeplatz in Zurich, Switzerland March 20, 2023.

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