This paper uses detailed information on U.S. banks' foreign claims to identify changes in the supply of cross-border funds due to the stance in U.S. monetary policy. We show evidence that during a monetary tightening U.S. banks significantly reduce their holdings of cross-border claims on foreign residents, supporting the existence of a cross-border bank lending channel. The result is stronger for banks with foreign offices. In addition, we test for the relevance of a balance sheet channel at the country level. We find that this mechanism is not significant, as we observe larger reductions in cross-border lending to "safer" countries than to those defined as "risky".