The 2016 Republican frontrunner has a large though not-yet insurmountable lead in the primary contests to choose the Republican Party’s candidate for the US presidency.
"I share the concerns about Donald Trump that my friend and former Republican [presidential] nominee Mitt Romney, described," McCain said.
"I would also echo the many concerns about Mr. Trump’s uninformed and indeed dangerous statements on defense and national security issues," McCain added.
McCain cited a letter signed by more than 75 US national security and foreign policy experts who pledged to abandon the Republican ticket if Trump is chosen as their party’s nominee.
Trump won seven of 12 states in the so-called Super Tuesday primary contest earlier this week, cementing his position as Republican frontrunner by a margin so great that it will be difficult, though not impossible, for any other candidate to prevail, according to US electoral math cited by political analysts.