The Greens are trying to have the Senate debate Australia's involvement in Iraq, saying there is no greater responsibility than sending personnel into war.
But the attempt is being opposed by the government and the opposition.
At the beginning of parliament on Monday, Greens leader Christine Milne moved to suspend standing orders to allow a debate in the upper house.
"I believe that it is time that the Australian parliament was brought into this debate," she said.
"There is no greater responsibility that a parliament has, that a prime minister has, than to send our armed service men and women into a war zone, into a war."
The move comes a day after Prime Minister Tony Abbott announced Australia would take part in an international airlift of military equipment to Kurdish forces fighting Islamic extremists in northern Iraq.
"We are into mission creep," Senator Milne warned.
Defence Minister David Johnston said a parliamentary debate on operational activities in Iraq would imperil lives.
What was occurring in Iraq had no comparison in recent history and only Kurdish forces had provided any significant resistance to the forces of the Islamic State, he said.
"We would not want to see that resistance fail for want of ammunition or other supplies.
"Were we to delay making decisions as the events confront us, people's lives will be seriously at risk as we have seen so far."
Opposition defence spokesman Stephen Conroy dismissed the Greens' move as "a stunt to score cheap political points".
And he rejected their view that parliament have a say in military deployments.
"Executive government is the most appropriate body to exercise civilian control of the Australian Defence Force," he said.
Former Labor defence minister John Faulkner agreed but said the government needed to be as open as possible in frankly explaining what was going on.
Senator Johnston needed to make a ministerial statement on activities in Iraq as soon as possible and that should be followed by a full debate in the Senate, he said.
"It is responsible, it is serious, it is open, it is consistent with past practice in this chamber."
Liberal Democrat David Leyonhjelm said any military deployment should require a two-thirds majority of both houses of parliament.
Although he supported the airlift of weapons to Kurdish forces, the decision was "too profound" to be left to government.
He also dismissed concerns that operations could be jeopardised by debate in the parliament.
"We are talking about the commitment of troops, not what they do," he said.
"It's whether they go at all."
Greens senator Scott Ludlam said Australia was practically at war because the operation was no longer humanitarian.
Parliament might well approve the operation but the government would be required to impose some boundaries.
"I suspect the reason that you won't do that is that we are once again ... acting at the behest of the United States government, not the people of Australia," Senator Ludlam said, citing the Korean, Vietnam, Iraq and Afghanistan wars as previous examples.
The motion was defeated 13-44 with Senator Leyonhjelm, independent Nick Xenophon and the Palmer United Party's Jacqui Lambie voting with the Greens.
In the House of Representatives, the sole Greens MP Adam Bandt failed in his bid to bring on a similar debate.