His comments came after the US Congress passed the most significant housing legislation in decades at the weekend.
The elaborate housing rescue plan is designed to help thousands of US homeowners avert foreclosure and bolster mortgage finance giants Fannie Mae and Freddie Mac that have struggled amid a volatile housing market.
The US Government on Friday shut down two more banks, taking the total to 10 that have been closed in the 18 months since the housing crisis first shuddered through the world's largest economy.
Locally, Australian bank shares were savaged on Friday after NAB (nab.ASX:Quote,News) booked an $830 million writedown on risky US mortgages.
NAB shares plunged more than 13 per cent in their biggest one-day fall since 1987.
"This is the bottom for us for housing in the US because we are now cleared out,'' Mr Stewart told ABC TV yesterday.
But he said "things are going to get worse'' for the US housing market.
"There are more than 18 million vacant properties for sale in the United States just now. That's more than the whole housing stock of Australia.''
Mr Stewart said even before the US housing crisis started, house prices were dropping as a result of over-stocking.
"They had just built too many houses, so the market was soft,'' he said.
In the US, people were literally walking away from their houses as their equity in them became negative.
"If that happens, continually happens, then these houses come on the market and, of course, they further depress prices,'' Mr Stewart said.
He said it was a worrying time for the US economy and it would be some time before it recovered.
Australian shares, which suffered their worst falls in six months on Friday, could open stronger today after Wall St recorded a slight rise overnight on Friday.
The Dow Jones Industrial Average lifted 21.41 points to 11,370.69.
US markets lifted on lower crude oil prices, a better-than-expected report on orders for durable manufactured goods, and a report showing only a modest decline in new home sales of 0.6 per cent in June.
CommSec chief equities economist Craig James said Australian investors had over-reacted on Friday to bad news from the NAB.
"I think our market can start out in the black (today), up by the order of 20 or 30 points . . . certainly the bargain-hunters will be looking out for those stocks that really didn't deserve the selling that was handed out to the market on Friday,'' he said.
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