The government is giving defence extra money this year and the next but reducing funding by more than $1 billion in the following two years.

Defence Minister Stephen Smith termed this a modest variation with defence contributing to the return to a federal budget surplus in 2016-17.

"We have moved a billion dollars out of that financial year, a modest adjustment out of an overall forward estimate spend of $113 billion," he told reporters in Perth.

"Whether it is facilities, estates, maintenance, or capability and equipment, there a lot of big projects and they will move around."

The economic statement on Friday says there will be an increased payment of $359 million to defence in 2013-14 and $304 million in 2014-15.

But in 2015-16, $89 million is cut, soaring to $1 billion in 2016-17. Then defence gets some more money, $426 million in 2017-18.

The government said this would better match expected capital acquisitions, support the purchase of important defence capabilities and accelerate investment in critical supporting capabilities and facilities.

That follows cuts to defence in the 2012-13 budget as the government sought to return to surplus.

When that proved impossible, defence got its money back, with funding of $25.4 billion in 2013-14, rising across the forward estimates to $30.7 billion in 2016-17, now set to be cut to $29.7 billion.

Opposition finance spokesman Andrew Robb said the government was returning to its notorious money shuffling, using defence in a bid to put the budget into surplus.

"This is a return to all the nonsense money shuffles that we have seen over the last couple of years," he said.

Opposition parliamentary secretary Gary Humphries said this made a mockery of government claims that defence faced no further cuts.

"We all know that a deferral is no better than a cut when it comes to defence spending," he said in a statement.