Prime Minister Tony Abbott has assured South Australians there will be more submarine jobs in their state even if he won't commit to having a new fleet of vessels built there.
Mr Abbott was responding to reports on Tuesday that some Liberal MPs fear a voter backlash against the coalition if the contract for Australia's next-generation fleet goes to Japan.
A competitive evaluation process is under way for the contract, which could also be given to France or Germany.
"Whatever happens, I can give an absolute, categoric guarantee there will be more sub jobs in South Australia and I think that's what South Australians understandably want," Mr Abbott told reporters in Sydney.
The process would deliver the best submarines at a fair and reasonable price, he said.
Earlier, parliamentary secretary Steven Ciobo conceded there was understandable concern from some of his SA colleagues about any decision.
But he accused Labor of "kicking the can down the road" for six years on naval ship building in Australia, referring to the absence of domestic contracts by the Rudd and Gillard governments.
Opposition frontbencher Brendan O'Connor claimed Mr Abbott had already done a secret deal with Japan.
Australia needed to predominantly build and maintain the fleet, otherwise the local manufacturing industry would be decimated, he told Sky News.
Independent Senator Nick Xenophon, who has been prominent in the push to get subs built in his home state, plans to field candidates in Liberal-held seats in SA in a bid to pressure the coalition.
"I'm working very hard to get a number of really credible, strong lower house candidates," he told Sky News from Japan.