Mitt Romney focused his fire on Hillary Clinton Sunday, repeatedly slamming her foreign policy record as “clueless” and predicting she will go down in defeat in 2016 because of it.

Clinton has no successes to point from her record as secretary of State, Romney said.

Her attempt to reset U.S. policy on Russia had the opposite effect, Romney said, and her recent comments regarding the Obama administration's release of five Taliban leaders from Guantanamo Bay in exchange for Sgt. Bowe Bergdahl, were “clueless.”

“She said the commandos don't represent a threat to the United States,” he told David Gregory, the host of NBC's “Meet the Press.” “Of course they do ... are you kidding?”

Romney held a three-day summit for 2016 Republican hopefuls in Park City, Utah this weekend. Clinton had a scheduling conflict and opted not to join the group of Republicans that included Sen. Rand Paul, Rep. Paul Ryan, Mike Huckabee, New Mexico Gov. Susan Martinez and New Jersey Gov. Chris Chris Christie.

With security in Iraq unraveling this week as al Qaeda-inspired Islamic State of Iraq and Syria took control of major cities in the North, Romney's position in his losing 2012 campaign against President Obama that the U.S. should leave a residual number of troops in the country to maintain stability has gained new attention.

When asked what he would do differently, Romney slammed Obama for waiting too long to make a decision about it.

“Bad things happen as a result of inaction – the consequences, obviously, have been very severe,” he said.

“The time [to act] in Syria was when [Bashar] Assad was on his heels,” he said, and the time to act in Iraq was when the Obama administration was negotiating a Status of Forces agreement, a deal to allow a residual number of U.S. troops to remain there, was taking place before all troops left at the end of 2011.

When asked what he would do differently now in Iraq, Romney said Obama needs to rely on U.S. intelligence resources, which he doesn't have access to, to make those decisions.