Australia's Westpac Banking Corp. this week issued A$1bn (US$899.9m) of prime residential mortgage-backed securities (RMBS). Moody's Investors Service assigned a triple-A provisional rating to the A$920m of Class A notes. "This deal is one of a number launched in the Australian RMBS market in recent weeks and comes without the support from the Australian Office of Financial Management (AOFM)," said Ilya Serov, Moody's lead analyst on the transaction. "It also marks the return of one of the four major Australian banks to the securitization market, further underlining improving confidence by both issuers and investors." The pool backing the transaction is almost three years seasoned, which Moody's said helps mitigate the risk of early payment default. The weighted average loan-to-value ratio is 58.28%, and all loans originated with full income verification, Moody's said. Unlike most Australian RMBS transactions -- where mortgage insurance supports the underlying pools -- only a small portion of the current pool underlying the Westpac deal is insured, Moody's said. Write to Diana Golobay.