Dec 2 (Reuters) - Westpac Banking Corp said on Wednesday it would sell its general insurance arm to German insurer Allianz for A$725 million ($534.5 million), further trimming its portfolio to beef up capital and focus on core banking.

Australia's third-largest bank also said it would sign a 20-year exclusive agreement for Allianz to distribute general insurance products to Westpac customers.

($1 = 1.3563 Australian dollars) (Reporting by Nikhil Kurian Nainan in Bengaluru Editing by Chris Reese)