Democratic presidential candidate Hillary Clinton on Sunday issued a more measured response to the implementation of the first phase in the Iran nuclear deal and the lifting of U.S. sanction by executive order.

“I have said for a long time that I’m very proud of the role that I played in getting us to the point where we could negotiate the agreement that puts a lid on Iran’s nuclear weapons program. But I’ve also said that the way we’re going to hold them accountable is to have consequences when they do anything that might deviate from the agreement or continue to flaut the kind of sanctions and mandates that the UN Secretary Council has put on, including on missiles,” Clinton said during an appearance on NBC’s “Meet the Press” program Sunday.

“This is a good day,” President Barack Obama started off in a rare address from the White House cabinet room on Sunday. “Yesterday marked a milestone in preventing Iran from obtaining a nuclear weapon. Iran has now fulfilled key commitments under the nuclear deal.”

But according to Hillary, “There’s more work to be done” in enforcing the nuclear deal as well as bring home Jewish-American Robert Levinson, who went missing in Iran nine years ago. “But if the implementation of the agreement which is being done today, is to be successful in the way that I expect, we’re going to watch Iran like the proverbial hawk,” she vowed.

Hillary also promised to immediately impose sanction on Iran if they violate UN Security Council restrictions on their missile program, as they have done twice in the past few months. “If they are violating it, which the evidence seems to suggest, they should be held accountable,” she said. “They need to know that this is a good step forward with respect to the nuclear weapons program. But there are other areas of their behavior that we’re going to continue to be focused on.”

Asked is she still considers Iran a national security threat to the United States, Hillary said, “Certainly we have lowered that threat, because of the nuclear agreement. But they continue to destabilize governments in the Middle East, they continue to support proxies and terrorist groups like Hezbollah. They continue to threaten Israel. There are a lot of concerns. But what I have said for some time now is I’d rather have the nuclear weapons program off to one side and work to make sure they abide by the agreement and then turn our attention to some of these other behaviors that are threatening certainly in the region, and therefore cause concern for us.”

Meanwhile, Republican presidential hopeful Marco Rubio, appearing on the same program, criticized the administration for the terms of the prisoner swap deal. “I don’t think these Americans should have ever been in prison. They didn’t do anything wrong. They are hostages. And so now we have a president that has traded hostages in exchange for prisoners who did commit a crime and were convicted after due process and a trial and everything of that sort,” said Rubio. “And what the President’s now doing, not just with this but what he did with the Castro brothers and what he did with Bergdahl, is he’s put a price on the head of every American abroad. Our enemies now know that if you can capture an American, you can get something meaningful in exchange for it.”

Rubio reiterated his pledge to reimpose sanctions on Iran on Day One, “and if Iran tries to build a nuclear weapon program, we will stop it.”