The share price of Barclays Plc – whose Barclay’s Global Investors division is the world’s largest issuer of ETFs – has been rocked by a large stock sale from a Middle Eastern investor. Shares in the troubled British bank have fallen 20% since Monday’s announcement that Abu Dhabi based Sheikh Mansour bin Zayed al-Nahyan sold his entire stake at a 17% discount. The share price slump further reduces Barclay’s capital base, already cut to perilously low levels by the financal crisis.

Barclays new financial troubles makes it much more likely the bank will seek to unload its iShares ETF division for a higher price than the one agreed to with private equity firm CVC Capital Partners. iShares was sold to the Boston based firm for USD 4.4 billion in April, but Barclays has until June 18th to seek a higher price under a “go-shop” clause of the contract.

Vanguard, Blackrock, and Bank of New York Mellon have all been rumored to be bidders.