Sen. Tom Cotton, a leading GOP critic of the Iran deal, said it's highly unlikely Iran will change its behavior and rein in its support for terrorists and other belligerent behavior to Israel, the United States and western allies.

To the Arkansas Republican, who served in the Army both in Iraq and Afghanistan, the issue is highly personal.

"If you think Iran is going to change their behavior in a decade, I can tell you how unlikely that is because just nine years ago, they were trying to kill me and my soldiers," he told Chuck Todd, the host of NBC's "Meet the Press." "We were lucky but hundreds of other American troops were not."

Cotton said the inspection and enforcement mechanism in the Iran nuclear deal, reached earlier this week, were too weak and denied that the U.S. and its allies don't have any alternative but to go along and accept the deal that was just negotiated.

"The alternative," he said, "is for Congress to reject this deal and demand a better deal — to send our negotiators back to the table with the threat of tougher sanctions and military force and get a better deal for the American people."

In March, Cotton penned an open letter to Iranian leaders signed by 46 other senators. The letter reminded the leaders that the U.S. Constitution requires the Senate to provide an advise-and-consent role to any major treaty, and said that any deal struck with administration negotiators could be undone either by Congress or the next president.

"The United States sanctions are what's always been what's most important here, and I'm confident that the American people as they learn more about this agreement, are repudiating it and that Congress will ultimately reject it," he said.

Todd also asked Cotton about his reaction to Donald Trump's criticism of Sen. John McCain's status as a war hero.

Cotton said he disagreed with them and recommended that he "apologize and retract" the remarks and "get back to the campaign that he's been running."

He also noted that McCain's father was high-ranking Navy admiral at the time of his imprisonment in Vietnam.

"The Vietnamese offered him early release in direct violation of the code of conduct for POWs," Cotton said. "John McCain declined that early release and obeyed the code of conduct, so I think we should all respect John McCain's service."