UNITED KINGDOM : 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 fell 0.8%, touching a two week low, while the more domestically-focused FTSE 250 midcap index lost 0.6%. Fitch on Tuesday downgraded the U.S. to AA+ from AAA, citing fiscal deterioration over the next three years and repeated down-the-wire debt ceiling negotiations that threaten the government's ability to pay its bills.

BAE Systems added 4.7% after Britain's biggest defence company upgraded its guidance for 2023, forecasting annual earnings per share would grow 10-12%. London-listed shares of Smurfit Kappa fell 3.0%, after Europe's largest paper packaging producer reported a fall in first-half core profit to 1.1 billion euros ($1.21 billion).

ConvaTec Group jumped 4.0% after the technology firm raised its full-year guidance.