Dozens of major Australian military purchases are billions of dollars over budget and years behind schedule, Defense Minister Richard Marles said, warning that the country faces "the most difficult circumstances" since World War II, Bloomberg reported.

Marles, who is also deputy prime minister, said 28 major projects are behind schedule, including Australia's new Hunter-class frigates and P-8A Poseidon aircraft. There have also been at least A$6.5 billion ($4.1 billion) in cost overruns on 18 projects, Marles said.

As a result, defense spending will rise to 2.2 percent of gross domestic product over the next decade, up from 2 percent last fiscal year, a higher proportion than in other Western countries, including Canada, France and Italy.

"Given the current strategic circumstances we face, we need to focus more on the quality of spending within defense to ensure that we provide our Australian Defense Force personnel with the best capabilities," Marles said.

The military has repeatedly faced challenges because of its equipment procurement and maintenance plans. Problems with the MRH90 Taipan helicopter fleet led Australia to request 40 Black Hawk helicopters from the U.S. to replace them, at an estimated cost of $1.95 billion.

While the sale was approved by the State Department in August, Marles said the government is still deciding whether to proceed with the purchase.