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* FTSE 100 down 0.1%, FTSE 250 off 0.2%

Sept 18 (Reuters) - UK's FTSE 100 slipped at open on Monday as investors await interest rate decisions from the U.S. Federal Reserve and the Bank of England (BoE), while Britain's main manufacturing trade body cut its forecast for the sector's growth for this year.

The exporter-heavy FTSE 100 slipped 0.1% by 0712 GMT, while the mid-cap FTSE 250 was down 0.2%.

Market participants keenly await the Fed's and the BoE's policy decisions as well as key domestic inflation data later this week as they hope for an end to the monetary tightening cycle.

Britain's main manufacturing trade body cut its forecast for the sector's growth for this year and next, citing a sharp fall in factory output and economic uncertainty.

Shares of Phoenix Group rose 1.6% after the life insurer said it expects 2023 cash generation to come in at the top end of its forecast range.

Mondi Plc jumped 4.9% after the paper and packaging firm agreed to sell its largest plant in Russia to a unit of Sezar Group, a Moscow-based real estate development firm, for 80 billion roubles ($825.7 million) in cash. (Reporting by Siddarth S in Bengaluru; Editing by Savio D'Souza)