Foreigners bought fewer long-dated U.S. securities in May and, including bills and other short-term instruments, were net sellers of all U.S. assets for the first time in 11 months, U.S. Treasury data showed Monday.

The United States attracted a net long-term capital inflow of $23.6 billion after $30.6 billion in April. Including short-dated assets such as bills, foreigners sold a net $67.5 billion, reversing the prior month's upwardly revised net inflow of $66.6 billion. The May tally was the first net outflow since June 2010.

Foreigners still increased net Treasury note and bond purchases by $14.6 billion. China, the largest foreign U.S. creditor, held $1.160 trillion in May, from $1.153 trillion.