RIGA (Reuters) - It is not the European Central Bank's job to stop cross border bank mergers, supervisory chief Claudia Buch said on Wednesday, just as Germany's Commerzbank was looking for ways to thwart a potential takeover approach by Italy's UniCredit.

"Whatever we can do within supervision is not to stand in the way of more cross-border integration," Buch told a conference in Riga. "Anything we can do within our remit to make sure that cross-border activity is not hampered, that we certainly do."

Some in German political circles hope that the ECB, whose approval is needed for any deal, would stop the transaction. But bank officials, including ECB President Christine Lagarde, have made clear that they see mergers as desirable.

(Reporting by Balazs Koranyi; Editing by Peter Graff)