Prime Minister Scott Morrison has played down suggestions of a preselection fight between Liberal powerbrokers in the federal seat of Curtin as election campaigning ramps up in Western Australia.

Key points: Liberal preselectors will decide on Sunday who will replace former foreign minister Julie Bishop

Liberal preselectors will decide on Sunday who will replace former foreign minister Julie Bishop Prime Minister Scott Morrison said suggestions of an internal battle by powerbrokers was "overstated"

Prime Minister Scott Morrison said suggestions of an internal battle by powerbrokers was "overstated" He is confident his government can retain five Liberal-held seats in WA at the election, despite a push by Labor

Liberal preselectors will decide on Sunday who will be the party's candidate to replace former foreign minister Julie Bishop in the blue-ribbon seat in Perth's western suburbs.

Former University of Notre Dame vice-chancellor Celia Hammond had been seen as the favourite, but some within the party now view the contest as wide open.

Foreign policy specialist Erin Watson-Lynn and resources executive Anna Dartnell are also considered serious contenders.

On the first day of a three-day campaign tour in WA, Mr Morrison said suggestions of an internal battle by Liberal powerbrokers over the preselection had been "overstated".

"There are a number of candidates, the pre-selectors will stand up on Sunday and make a decision," he said.

"They will make a good one."

Federal Labor MP Madeleine King said it was "desperately unfortunate" if Curtin nominees were caught up in an internal preselection war.

"They did not sign up for this kind of internal brawl within the Liberal Party over who runs the preselection process and who should choose who sits in Curtin," she said.

"I have some sympathy for those Liberal candidates."

Labor believes it can win up to five Liberal-held WA seats at the coming federal election, targeting Swan, Pearce, Hasluck, Stirling and Canning.

But Mr Morrison has said the Government can hang on to all five seats, and also signalled a push to win back the seat of Cowan, held by Labor's Anne Aly.

Anne Aly says she is not concerned about the Prime Minister campaigning in her seat of Cowan. ( ABC News: Matt Roberts )

Dr Aly said she was not concerned, despite winning on a slim margin of 0.7 per cent at the last election.

"Bring it on," she said.

"I'm not worried about the Liberal Government, I'm not worried about Scott Morrison [campaigning] in Cowan."

In response to a funding wish list from WA Premier Mark McGowan, which included extra money for the planned urban rail network Metronet and regional roads, the Prime Minister talked up his part in delivering the state a fairer GST deal.

"They [the WA Government] have got to spend the money we have already sent them," he said.

"They have not even yet been able to spend the money on Metronet that we have committed to them.

"On this visit I have come with $1.3 billion to honour the GST arrangement I put in place. Too much money never seems to be enough sometimes with state premiers."