Middle East and Asian sovereign wealth funds will bring their investment in the world’s leading banks to more than $50bn (€33.5bn) if plans by Citigroup and Merrill Lynch to tap them for the second time in as many months come to fruition.

Banking sources said Merrill Lynch and Citigroup, which are expected to announce further losses this week due to the US sub-prime crisis, are seeking around $18bn of outside capital, of which $14bn is expected to come from China and Kuwait.