Tom Cotton, one of the Senate's biggest critics of the Iran nuclear talks, warned Sunday that "whatever deal comes out of this weekend, it's going to be dangerous for the United States and dangerous for the world."

Cotton, a Republican senator from Arkansas, appeared on CBS' "Face the Nation" just as U.S. diplomats told CBS news that there is momentum toward a nuclear deal with Iran and they should know by tonight if one will be possible. Talks have dragged out nearly two weeks past an initial June 30 deadline for a final agreement.

He made headlines earlier this year when he authored a controversial letter to Iranian leaders warning that Congress could undo any deal they made with President Obama. Despite backlash from Secretary of State John Kerry and others, Cotton defended his actions and said he had "no regrets at all."

Now, his principle concern is that the U.S. has "gone way too far down the road of making concessions to Iran." He said the U.S. has strayed from the original goal of stopping Iran from enriching uranium and developing their nuclear weapons capability, and said the U.S. should have abandoned the talks a long time ago.

When host John Dickerson asked what would happen if the U.S. stopped negotiating, ratcheted up sanctions, and Iran began racing toward building a nuclear bomb, Cotton said, "it really raises the fundamental question about the credible threat of military force" because the president has not taken military action off the table.

"The real question is whether the Iranians take him at his word. I'm afraid they don't, because they've seen time and time again that the window for diplomacy with this president and this administration never ends. You're not really negotiating if you're not willing to walk away from the table. You are only giving more and more concessions, teaching the Iranians a very bad lessons," Cotton said. "That's why I think we should've walked away from the table a long time ago and pressed the pause button to get back to that original goal of stopping Iran from developing any nuclear weapons capabilities."

He argued that by simply engaging in negotiations, making concessions to Iran and not pushing them to release American citizens from prison, the U.S. has elevated Iran's role in the region. Cotton also said the nuclear talks have limited America's willingness to work with Sunni Muslims and Kurds in Iraq to defeat the Islamic State of Iraq and Syria.

Cotton was laser-focused on Iran throughout the interview, even when asked about incoming Chairman of the Joint Chiefs of Staff Joseph Dunford's assertion that Russia is the number one existential threat to the U.S.

"I think Russia is a serious threat. And the reason they're such a serious threat is they still remain the one country with the capability of destroying the American way of life, because of the legacy nuclear weapons systems they have from the Soviet Union," Cotton said. "But we can't let Iran get the same capability, since Iran has clearly demonstrated the intent to destroy America."