Australian Trade Minister Mark Vaile is locked in talks with US Trade Representative Robert Zoellick in Washington, with the two sides already overrunning a deadline to seal a deal by the end of 2003.

Talks were due to be wound up by Friday but a spokesman for Vaile said negotiations would continue over the weekend in a race against time to clinch a deal to put to the US Congress for approval before November's presidential elections.

"The talks will be continuing over the weekend," said Vaile's spokesman. "The minister will remain in these negotiations as long as he feels progress is being made."

No further details about the progress in talks or the major obstacles were available.

Free-trade negotiations between Canberra and Washington began last March and were made a top priority of President George W Bush's administration following Australia's backing of the US led invasion of Iraq.

Australia is pursuing a free trade pact with the United States, its second largest trading partner, as analysts believe it could boost the domestic economy by A$4 billion a year. Two-way trade is now worth A$28 billion ($20 billion) a year.