Rating agency Moody's sees no immediate threat to Australia's triple-A rating from tumbling commodity prices that have prompted some miners to scrap planned investments and cut output.

Prices for iron ore and coal, Australia's two largest exports, have fallen sharply in recent weeks, raising concerns about the impact on Australia's terms of trade and tax revenues if the slump is prolonged.

"We are very comfortable with Australia's triple-A ratings because of the government's very low debt levels compared with other sovereigns in the triple A category," Steven Hess, a senior vice-president at Moody's in New York, said.

The resource-rich country is one of just 10 nations with a top-notch rating and stable outlook from Moody's.

To the envy of many Western nations, Australia's net debt is expected to be 9.2 per cent of gross domestic product in 2012-13, a fraction of that of Japan or Europe.