Investors have pulled more than $400bn from money market prime funds in the past two months, leaving the funds waiting urgently for a Federal Reserve rescue plan to help them sell commercial paper to meet redemptions.

The Fed said on Monday that it would begin the rescue plan on November 24, a few weeks later than planned. Money market funds are low-risk, low-return funds that normally invest heavily in commercial paper, a type of debt used by businesses to meet short-term funding needs.