In April, Sudan and South Sudan slipped close to all-out war with a series of tit-for-tat air raids and ground attacks that prompted the African Union and Security Council to push the two sides to act.
In response, Gingrich said his attacks were only the initial salvos of an all-out assault on the issue that Romney would face from the Obama campaign if he became the nominee.
Republicans are outraged at what they regard as Mr Berger's vindictive, partisan and intellectually shallow attacks, pointing out the absurdity of labelling all Republicans as isolationists when opponents of the test-ban treaty included many of the most internationally-minded senators.