Berenberg Bank upgraded its rating for BAE Systems from 'hold' to 'buy' and said the company's Saudi market opportunity has been over looked.The bank lifted its price target for the UK's biggest defence firm from 461p to 570p, in a note to investors.Berenberg said more activity in Saudi will generate an upside which was presently overlooked by the market.Saudi's air fleet will expand and drive this upside as the country embarked on new 'self-determinist' foreign policy, the bank said.BAE Systems' current contracts with Saudi could be extended and upgrades requested as activity ramps up.Berenberg also noted UK defence cuts would have minimal impact on the company.Shares in BAE systems had lifted 1.05% by 10:23 on Friday to 472.10p.