The United States is paying to store its own military weapons on Australian soil at the Tindal RAAF Base.
Several residents have questioned the Katherine Times on the building of magazines at Tindal.
What ordnance the magazines might contain is being kept secret.
The weapons storage areas and a new jet "fuel farm" at Tindal have been planned for more than a decade as part of joint training programs between the US and Australia.
While COVID-19 restrictions have stopped most joint exercises this year, the Tindal base's runway is being extended so KC-30A Multi Role Tanker Transport can use it and it can accept bigger US military aircraft like B-52 Stratofortress bombers.
Other "joint initiatives" for Tindal are also being planned, a Defence Department spokeswoman said.
The United States Naval Facilities Command Pacific has announced a $15.01 million contract for the building of earth covered magazines at Tindal.
The magazines "will be used by the US in accordance with Force Posture Agreement", the spokeswoman said.
"The project will construct two Earth Covered Magazines and a production area that will include a munitions assembly conveyor shelter to support United States and Australian military joint training activities."
In a prepared statement late last week, the US Naval Facilities Engineering Command Pacific announced the building program.
"The NAVFAC Pacific Team is excited to extend our strategic partnership with the Australian Government and US Air Force three hours south of Darwin to the city of Tindal," NAVFAC Pacific operations officer Capt. Tres Meek said.
"United in purpose, we will deliver increased warfighting capability through our trusted construction community in the defense of freedom. Let's start building!
"This Asia-Pacific Resiliency project provides adequately sized, structurally sound, and safe munitions storage capacity in the form of earth covered magazines.
"This project supports plans outlined by the bilateral United States/Australia Force Posture Agreement and enables Bilateral Enhanced Air Cooperation missions."
The Force Posture Agreement is a post ANZUS military treaty signed between the US and Australia in 2014 following an announcement made during the visit of then US President Barack Obama and Australian Prime Minister Julia Gillard in November 2011.
Then PM Gillard said: "... we have agreed (to) greater access by US military aircraft to the Royal Australian Air Force facilities in our country's north. This will involve more frequent movements of US military aircraft into and out of northern Australia."
"It will mean that we are postured to better respond together, along with other partners in the Asia Pacific, to any regional contingency, including the provision of humanitarian assistance and dealing with natural disasters," Ms Gillard said.
The Force Posture documents sate: "With full respect for Australian sovereignty and the laws of Australia, United States Forces and United States Contractors shall have unimpeded access to and use of Agreed Facilities and Areas for activities undertaken in connection with this Agreement. Such activities may include: training, transit, support, and related activities; refuelling of aircraft; bunkering of vessels; temporary maintenance of vehicles, vessels, and aircraft; temporary accommodation of personnel; communications; prepositioning of equipment, supplies, and materiel; deploying forces and materiel; and such other activities as the Parties may agree."
In regards to what the Tindal magazines might contain.
"Procedures on what capabilities visiting forces may or may not have in Australia is covered by government procedures," the Defence spokeswoman said.
"Defence will continue to comply with government interpretation of Australia's obligations under the South Pacific Nuclear Free Zone Treaty and the non-proliferation treaty."
Building of the Tindal magazines are expected to complete by February 2022.
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