Sydney - Australia's securities regulator Sunday joined the United States, Britain, Germany, France and Switzerland in curbing the short-selling of shares.

In a short sale, a trader sells borrowed stock, hoping to make a profit by buying it back at a cheaper price.

Many argue that short-selling is behind the turmoil in global share markets. They claim hedge funds are deliberately driving down the price of shares in order to make windfall profits when they buy them back.

Last week the Australian Securities and Investments Commission (ASIC) ruled that from Monday a temporary ban on what's called naked short-selling would take effect. In naked short-selling, traders sell shares they don't actually own.

Now, ASIC has extended that temporary ban to include covered short-selling. Covered short-selling is where the seller borrows shares for a fee and pays them back in the same stock at a later date.

"The measures being taken by ASIC are an appropriate response to global financial market turbulence," Treasurer Wayne Swan said in a statement.

Opposition Liberal Party leader Malcolm Turnbull, a former merchant banker, has urged Prime Minister Kevin Rudd to cancel a trip to New York this week where he is to address the General Assembly.

Turnbull, who was elected leader only last week, said Rudd should be at home to deal with the financial crisis. He pointed out that Rudd, who has been prime minister for 
300 days, has spent 50 of those days outside Australia.

It's also Rudd's second visit to the US since becoming leader in November.

Rudd, who leaves Monday, was adamant that his trip was still on.

"By definition, a global financial crisis requires a global response and that means if you've got more than 100 heads of government in New York for three days," Rudd told local television, adding that "the number one topic for debate among heads of government will be the content of a further global response to the global financial crisis."

Turnbull insisted Rudd should stay. "This is not about 100 world leaders in New York or big banks," he said. "This is not about Wall Street. This is really about Main Street. This is about real people, their savings, their lives." (dpa)