Barclays dropped almost 5% after Qatar's sovereign wealth fund said it was selling half of the warrants it holds in the bank.Qatar Holding is selling 379.22m shares that it is converting from warrants at an exercise price of 197.775p each, but said it will remain a long-term shareholder in the bank. The placing will be arranged by Credit Suisse today.Speculators have put two and two together and surmised that the Barclays sale could be a prelude to Qatar making a renewed assault on supermarket group Sainsbury, where it has a 26% stake. The two parties had a protracted courtship during 2007 which ended with the sovereign wealth fund opting not to make a bid for the UK's third largest supermarket group. 'The decision to exercise the warrants and dispose of the resultant shares forms part of Qatar Holding's portfolio management program and does not impact on our current intention to remain a long term strategic shareholder in Barclays,' said Ahmad Al-Sayed, chief executive and managing director of QH.Barclays' chief executive John Varley added: 'We are happy to be working with Qatar Holding on a placing derived from the exercise of some 50% of its warrants. The effect will be further to broaden the base of our share register.'Barclays shares are currently down 4.95% at 363.15p.