Australia's first woman Prime Minister Julia Gillard, who came to power three weeks ago after the ouster of Kevin Rudd, has called a general election for August 21, launching a bitter campaign over issues like asylum seekers, economy and global warming.The election announcement came after Gillard, 48, of Labour party met Governor General Quentin Bryce and requested him to dissolve Parliament and set the poll date for either August 21 or 28, giving a time frame of five weeks for campaigning.Opposition leader Tony Abbott, meanwhile, claimed that his Coalition can deliver stability as he unveiled an election-eve pledge to make no change to workplace laws for at least three years if he becomes Prime Minister. The Coalition needs to gain 17 seats with a uniform 2.32 per cent swing to win the election.It will be the first winter campaign since Bob Hawke won in 1987 and the first August poll since John Curtin's 1943 victory.