During a parliamentary address last week, Christopher Pyne confirmed that he spoke with Mattis to congratulate him on his recent appointment and to express his and the Australian government's commitment to the two countries' defence alliance.
"I expressed my enthusiasm and strong desire to work closely on our shared defence interests as a key ally of the United States," Minister Pyne said.
Minister Pyne said Secretary Mattis also reciprocated these sentiments, along with his support for the Joint Strike Fighter program for the US and their allies.
"Secretary Mattis reiterated his strong support for the Joint Strike Fighter program as a key strategic capability for the United States and allies across the globe," Minister Pyne said.
"We talked about the fact that the price for the lot 10 of the Joint Strike Fighter has been recently announced and has dropped below $100 million for the first time. For Australia this is hugely significant and represents a 25 per cent reduction from the price of the fighter in 2014, showing the program is on track in terms of delivery and efficiency."
These statements came after a tumultuous week of headlines dominated by Prime Minister Malcolm Turnbull's phone call with President Donald Trump.
Details of an acrimonious phone call between the two leaders emerged, in which Trump allegedly described the phone call as his "worst call by far", along with a tweet from Trump describing a pending US-Australia refugee deal as a "dumb deal".
This led to many experts commenting and worrying about strained relations between the two allies and geo-political and defence ramifications.