The London Stock Exchange Group offices are seen in the City of London, Britain, December 29, 2017. REUTERS/Toby Melville/File PhotoSummaryCompanies FTSE 100 down 0.8%, FTSE 250 off 0.6%Aug 2 (Reuters) - UK's FTSE 100 opened lower on Wednesday, as global risk sentiment took a hit after ratings agency Fitch cut the United States' credit rating, while BAE Systems shares jumped after the defence company raised its full-year guidance. By 0709 GMT, the bluechip FTSE 100 index (.FTSE) fell 0.8%, touching a two week low, while the more domestically-focussed FTSE 250 midcap index (.FTMC) lost 0.6%. BAE Systems (BAES.L) added 4.7% after Britain's biggest defence company upgraded its guidance for 2023, forecasting annual earnings per share would grow 10-12%. ConvaTec Group (CTEC.L) jumped 4.0% after the technology firm raised its full-year guidance.

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Persons: Toby Melville, Fitch, Shashwat Chauhan, Rashmi Organizations: London Stock Exchange Group, City of, REUTERS, BAE Systems, AAA, Smurfit Kappa, ConvaTec, Thomson Locations: City, City of London, Britain, United States, London, Bengaluru