BlackRock is scrambling to seal the purchase of Barclays Global Investors and see off an 11th-hour challenge from Bank of New York Mellon.

Barclays is expected to take a decision early this week on who should buy the BGI unit. If BlackRock did succeed, people in London briefed on the deal said Barclays was likely to take a stake of up to 20 per cent in the US money manager.