Scott Morrison has promised a helping hand to reduce the cost of living pressures as he prepares to deliver his second budget on Tuesday.

"We understand that families, households, individuals are under a lot of stress because they just haven't seen their wages going up," the treasurer told 9NEWS political editor Laurie Oakes today.

Aged pensioners, disability support pensioners, veterans and those on single parent payments will get a one-off payment to help with this winter's power bills.

Singles will receive $75 by June 30 and couples $125.

There will also be a $350 million boost to help defence force veterans battling mental health conditions, a decision that was quickly endorsed by deputy Labor leader Tanya Plibersek.

"We support anything that helps our veterans who have sacrificed so much for their country," Ms Plibersek told reporters in Sydney.

The federal government has also struck a $2.3 billion deal with the new West Australian Labor government in a road and rail package for the state that will create 6000 jobs as a result of 17 new projects.

Transport and Infrastructure Minister Darren Chester indicated there would be funding in the budget for the inland freight rail network between Brisbane and Melbourne.

"It is a very exciting project. It is one that's long overdue," he told ABC television.

Mr Morrison also hinted at a major health announcement in the budget, coat-tailing the government's schools and university funding plans last week.

He said Health Minister Greg Hunt had been working with the clinics, the medicine sector, pharmacists and doctors to ensure the budget delivered a "healthy Australia".

"This budget is all about making the right choices," he said.

"The choices you have to make are about growing the economy but they're also about ensuring the services that Australians rely on, and Medicare and the PBS these are critical services."

Shadow treasurer Chris Bowen said it looked like the budget was adopting "pale imitations" of Labor policy in an attempt to save the prime minister's political life.

"It is designed to save Malcolm Turnbull's leadership, desperate to get a positive Newspoll," Mr Bowen told ABC television.

Mr Morrison hit back at critics who say the commonwealth government can't make a difference to housing affordability and have accused the treasurer of wrongly raising expectations.

"I don't agree with the cynics," Mr Morrison said.

He said there would be a comprehensive plan that worked with the states and territories in the budget.

"It will address everything from the needs of those who don't even have a roof over their head to those who are trying to buy one to put over their head," he said.

"It will deal with those later in life who are looking to change their own housing arrangements."

Global credit rating agencies will be closely watching the budget.

Finance Minister Mathias Cormann said the government values the nation's triple-A rating, but in the end it will be up to the agencies whether it remains intact.

"We always work to ensure that our budget is in the best possible position and on the best possible trajectory for the future," he told Sky news.