John McCain John Sidney McCainThe electoral reality that the media ignores Kelly's lead widens to 10 points in Arizona Senate race: poll COVID response shows a way forward on private gun sale checks MORE on Thursday joined fellow former Republican presidential nominee Mitt Romney to blast current party front-runner Donald Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE.

The Arizona senator said he has the concerns about Trump that Romney expressed during a blistering speech on Trump's failed business ventures and vision for the country.

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"I would also echo the many concerns about Mr. Trump’s uninformed and indeed dangerous statements on national security issues that have been raised by 65 Republican defense and foreign policy leaders," McCain said in a statement.

McCain, who sits on the Senate Armed Services Committee, mentioned international threats facing the U.S. from countries including Russia, China, Iran and North Korea.

"I want Republican voters to pay close attention to what our party's most respected and knowledgeable leaders and national security experts are saying about Mr. Trump," McCain said.

The 2008 Republican presidential candidate called on voters to "think long and hard" about their chose for commander in chief, drawing into question the real estate mogul's credentials on the issue.

Romney, the 2012 GOP nominee, went after Trump's foreign policy credibility during his speech at the University of Utah, where he characterized the controversial billionaire as lacking the temperament to be president.

He also referenced Trump's mocking last year of McCain's capture during the Vietnam War.

Trump ripped Romney as a "failed candidate" ahead of his speech, pointing out that Romney took his endorsement when he ran for president.