According to the DSCA, Australia's government asked to buy 29 Apaches and associated equipment -- including spare parts, Hellfire Captive Air Training Missiles, M230E1 + M139 AWS automatic gun -- as well as training and logistical support.

The prime contractors in the the program will be Boeing and Lockheed Martin, the DSCA said.

"The proposed sale will improve Australia's capability to meet current and future threats, and will enhance interoperability with U.S. forces and other allied forces," the DSCA's announcement said. "Australia will use the enhanced capability to strengthen its homeland defense and provide greater security for its critical infrastructure."

Australia's defense ministry announced the request in January, saying the AH-64E Apache Guardian would replace its Airbus Helicopters Tiger fleet as its next armed reconnaissance helicopter.

"The Apache Guardian is the most lethal, most survivable and lowest-risk option, meeting all of [the Department of] Defence's capability, through-life support, security and certification requirements," defense minister Linda Reynolds said in a statement at the time.

Australia joins 17 countries -- including India,the United Arab Emirates, Qatar and Britain in flying Apaches.