The critical minerals strategic reserve is designed to break Beijing's grip on the supply of the metals needed for defence equipment such as fighter jets, and clean energy technology.
Dr Chalmers will travel to Washington DC this week to join a meeting of finance ministers from the G7 nations to discuss critical minerals.
The government will announce the metals antimony and gallium as the first to be the focus of the reserve, which Australia has argued can become a reliable supply of rare earths for the US.
US Treasury Secretary Scott Bessent is hosting the gathering for the group of advanced economies, which includes Japan, the UK, France, Germany and Canada, many of which depend on supplies from China.
Antimony is used in batteries and night vision equipment, while gallium is used for advanced semiconductors and radar systems.
Dr Chalmers said a reliable reserve would strengthen supply chains and help stabilise markets.
"The world needs critical minerals, Australia has plenty of them and our critical minerals reserve will help us weather global economic uncertainty and help to boost trade and investment," he said.
Resources Minister Madeleine King said the stockpile would support mining and processing projects.
"The strategic reserve's initial focus on antimony, gallium and rare earths will give added certainty to Australian projects, help attract further investment and help the sector deal with potential future market disruptions," she said.
Canberra and Washington struck a $13 billion rare earths deal in 2025 for a pipeline of projects to expand mining and processing in Australia.
The two countries committed to investing at least $1.5 billion each to develop critical minerals projects in the next six months.
