The phrase "partner nations" refers to countries or nations that work together and have a close relationship to achieve common goals or solve problems. They are like friends or allies who cooperate and support each other. Full definition
The Army is setting up six of these units, which are charged with advising and assisting partner nations in the development of their security forces. (wrvo.org)
His bill (H.R. 4698) would authorize the U.S. Transportation Security administration to donate security equipment to those overseas airports and increase cooperation with partner nations. (syracuse.com)
No, I don't think Myanmar is in a position to do anything to the U.S., but China and Russia are collecting quite the stable of partner nations who don't like U.S. actions or policies, and China especially is loving the fuel resources housed there, so giving everybody another reason to rally against us is not in our best interest. (dotearth.blogs.nytimes.com)