MELBOURNE, May 11, 2009 (AFP) - Australian Prime Minister Kevin Rudd on Monday defended spending policies poised to tip the budget into the red, saying the global recession had forced governments worldwide to increase borrowing.

The government is expected to unveil a deficit of about 70 billion dollars (52 billion US) in Tuesday's annual budget, the largest in the country's history and a huge turnaround from the 20 billion surplus forecast last year.

Rudd said the global financial crisis had left the private sector "in retreat" and governments had to step in to help offset the impact of recession, even if it meant going into deficit.

"Governments around the world are investing in short, medium and long term infrastructure," Rudd told reporters.

"All to support jobs, apprenticeships and training opportunities while building and investing in the nation building infrastructure we need for tomorrow.

"That's our strategy, we think it's the right strategy for Australia."

Rudd's centre-left Labor government estimates the global recession will cut 200 billion dollars from government revenues over the next four years.

It has also spent more than 50 billion dollars on stimulus measures and is expected to announce another 25 billion for infrastructure projects in the budget, meaning deficits are likely for at least the next five to six years.

But Deputy Prime Minister Julia Gillard said the government would eventually return the budget to surplus by reining in recurrent spending, even if that meant adopting "tough measures" that may be unpopular.

"We've been very clear that our task is to stimulate the economy whilst the economy is weak, and then, when the economy returns to growth, we obviously will be working hard to return the budget to surplus," she told CNBC television.

"We will be laying out a strategy about returning the budget to surplus on budget night."

But opposition frontbencher Peter Dutton told reporters: "This is going to be a big-taxing, big spending (budget), putting huge debt on a future generation."