Prime minister rejects the statement that Australia is ‘at war’, saying it is an ‘essentially humanitarian mission’

Tony Abbott has warned Australia’s involvement in Iraq would be dangerous and “quite lengthy” after cabinet authorised Australian airstrikes in Iraq against the Islamic State (Isis) group.

The prime minister refused to put a timeframe on Australian airstrikes, which will begin in days when RAAF planes join international forces.

Approval has also been given for Australian special forces troops to “advise and assist” Iraqi forces, though the legal framework is still being finalised.

Australia joins the US, UK, France and a number of Arab nations including Jordan, UAE, Bahrain and Qatar, in an international coalition of forces to fight the terrorist group.

“I have to warn that this deployment to Iraq could be quite lengthy, certainly months rather than weeks,” Abbott said. “I want to reassure the Australian people that it will be as long as it needs to be, but as short as it possibly can be.

“I also need to warn the Australian people that this is a dangerous mission. It is a dangerous mission, but I am confident that the CDF [chief of the defence force] has put in place all possible measures to minimise risk.”

The prime minister confirmed he had briefed the opposition leader, Bill Shorten, on Australia’s military involvement and welcomed Shorten’s support on national security – an area in which he said the government and the opposition should “stand shoulder to shoulder”.

Shorten said he was confident Australian military forces were capable of working out the rules of engagement and said he did not believe the involvement would increase the danger to Australia.

“I don’t believe if we did nothing there would be no threat of terrorism in the world,” Shorten said. “This is a sensible decision in a difficult set of circumstances.”

Six Australian F/A-18F Super Hornet aircraft are in the Middle East to take part in airstrikes, though cabinet has given approval for eight. The Super Hornets will join the Wedgetail early warning and control aircraft and a refuelling aircraft already supporting coalition operations over Iraq.

Abbott rejected the statement that Australia was “at war”, saying it was an “essentially humanitarian mission”.

“I know that you’d love to have that headline, but it’s not strictly accurate,” he said. “Yes, we are engaged in combat operations, but these are combat operations against an insurgency, in support of the legitimate government of Iraq. So we are not in combat against another country.”

The Greens and others have been critical of the government’s refusal to set out any end strategy. The Greens leader, Christine Milne, said Abbott was sending Australians to another war in Iraq “with a claim that following the United States is in our national interest”.

“The Greens stand with those Australians who are asking why is it in Australia’s national interest to join in another war in the Middle East without a clear strategic objective or risk assessment?” Milne said. “How will this war make us safer? Won’t it make us a bigger terrorism target and a more attractive recruiting ground for jihadists?”

Abbott said Australia had long been a terrorist threat, as shown by the Bali bombings in 2002, which killed 88 Australians.

Asked how the government would know when the mission had been successful, Abbott said: “We will know that we are succeeding, when Isil [Isis] are in retreat, not in advance.

“We will know that we are succeeding when the Iraqi government is restoring a modicum of control over its own cities and towns.

“We’re not trying to build liberal pluralism in Iraq, we’re not trying to create a shining city on a hill, we are simply acting as part of the US-led coalition in support of the legitimate elected government of Iraq. That’s all we’re doing.”

The chief of the defence force, Mark Binskin, said Australian special forces would be working on the ground, but behind the lines with Iraqi forces in concentrated units.

“They will be helping Iraqi forces with the planning and coordination of operations,” Binskin said. “It’s not envisaged that we will be engaged in combat operations ourselves but we will be advising and assisting the Iraqi forces as they, the Iraqi forces, engage in combat operations.”