The North Korean nuclear threat topped the agenda during Defence Minister Marise Payne's bilateral talks with her US counterpart.
Senator Payne met US Defense Secretary Jim Mattis at the Pentagon in Washington DC on Thursday (Wednesday US time.)
As well as the ongoing fight against Islamic State militants in Syria and Iraq, the pair also discussed the South China Sea maritime boundary dispute.
"You are a trusted ally who tells us what we need to hear, not what we might want to hear, and that's the mark of a true friend and one always worth listening to," Mr Mattis said in his opening remarks.
"I know our two nations will stand together in defence of freedom and liberty."
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He said the US looks forward to commemorating 100 years of "mateship" with Australia in 2018.
"The Australia-US defence alliance is absolutely ironclad, forged by 65 years of mutual trust, respect earned on the battlefield, and friendship across the sea," he said.
Senator Payne was expected to discuss Australia's role in the war in Afghanistan during the visit.
The Turnbull government has not ruled out increasing Australia's military commitment to Afghanistan after US President Donald Trump unveiled his new war blueprint in late August.
In May, Australia's government made a modest boost of 30 to its mission, bringing the total troops in Afghanistan to 300.
