Bad debt charges "are likely to rise from cyclical lows," Fitch Ratings said in a review of Australia's major banks.But it said "a material deterioration in asset quality is unlikely, absent a significant external event, such as a hard landing in China."The dynamics of the housing price cycle is the only real sore spot for Fitch.It said: "A further material and more widespread increase in house prices, particularly if coupled with a weakening of underwriting standards, leaves bank asset quality susceptible to deterioration, especially if unemployment were to rise substantially."Fitch Ratings has affirmed the AA- ratings of Australia's four major banking groups. The outlook on each bank is stable.