The 10 biggest prime U.S. money market funds cut their holdingsof debt issued by euro-area banks by $8.3 billion in May asconcerns mounted that the 17-country currency union could breakup.

The funds reduced holdings of Dutch banks by $3.3 billion lastmonth, while those in German banks declined by $2.9 billion and inFrench banks by $2 billion, according to data compiled byBloomberg. Funds increased holdings issued by Japanese, U.S. andU.K. banks by a combined $11.2 billion.

Holdings of debt from European banks, including those outsidethe euro region, have fallen every month since the end of January,with a combined decline of $20 billion over the period to $178billion. Elections in Greece have fueled concern that the countrymay exit from the euro, and Spain this month requested as much as100 billion euros ($126 billion) from European Union rescue fundsto recapitalize its banks. The country's credit rating this weekwas cut three steps by Moody's Investors Service, which cited thenation's debt burden.