Sydney - Australia Liberals squared off for another bruising round of infighting Monday when Brendan Nelson shocked them by putting his leadership on the line.

Liberal lawmakers meet Tuesday and are expected to either vote Nelson back into office or endorse economics spokesman Malcolm Turnbull as the new party leader.

Nelson has been leader since John Howard's coalition fell in a Labor landslide in November and Kevin Rudd became prime minister.

"I am asking our party to draw a line in the sand and mark a transition from the difficult aftermath of an election defeat to the building and presentation of a credible, attractive and inspiring alternative government," Nelson said in a statement.

Nelson triumphed over Turnbull in a close party-room vote nine months ago but trails behind Rudd in the opinion polls.

Nelson is hoping to capitalize on Peter Costello's confirmation at the weekend that he wouldn't challenge for the leadership and would likely be gone from Parliament before the next election. Costello served as finance minister for a record 11 years under Howard.

His decision not to accept an open offer to take over the party leadership pits Nelson, a former medical doctor, against Turnbull, a debonair former barrister and merchant banker. (dpa)