Democratic presidential hopefuls Hillary Clinton and Bernie Sanders outlined their differences on going forward with the Iran nuclear deal just a day after the U.S. lifted sanctions on Iran.

During the Democratic presidential TV debate in Charleston, South Carolina Sunday evening, Sanders expressed his desire to see the U.S. move forward to restore diplomatic relations with Tehran, while Hillary appeared more skeptical of Iran changing its behavior as a result of the nuclear deal implementation.

“I think what we’ve got to do is move as aggressively as we can to normalize relations with Iran,” said Sanders. “Understanding that Iran’s behavior in so many ways is something that we disagree with; their support terrorism, the anti-American rhetoric that we’re hearing from of their leadership is something that is not acceptable. On the other hand, the fact that we’ve managed to reach an agreement, something that I’ve very strongly supported that prevents Iran from getting a nuclear weapon and we did that without going to war. And that I believe we’re seeing a fall in our relationships with Iran is a very positive step. So if your question is, do I want to see that relationship become more positive in the future? Yes.”

“Can I tell you do I think we should reopen an embassy in Tehran tomorrow? No, I don’t think we should,” the Jewish Senator from Vermont added. “But I think the goal has got to be, as we have done with Cuba, to move in warm relations with a very powerful and important country in this world.”

Hillary poured cold water on that optimistic declaration. “They have been so far following their requirements under the agreement, but I think we still have to carefully watch them,” she said. “We’ve had one good day over 36 years, and I think we need more good days before we move more rapidly — before more normalization. And we have to be sure that they are truly going to implement the agreement, and then we have to go after them on a lot of their other bad behavior in the region.”

The debate continued off-air, as the Sanders campaign claimed that Hillary opposed negotiations with Iran in 2008. In a fact-checking email sent out during the debate, the Sanders campaign stated, “The last time Hillary Clinton attempted a run for president she was highly critical of then-candidate Barack Obama’s support of engaging with countries hostile to the United States. After Obama said in a debate that he would be willing to meet with the leaders of Iran, Cuba, and other countries — an approach that has since yielded a deal to peacefully remove Iran’s nuclear weapons and an opening up of relations with Cuba — Clinton called Obama “irresponsible and frankly naïve. Clinton’s campaign later said that doing so would be a “mistake.”

The campaign also highlighted Clinton criticizing Obama over his willingness to engage in diplomacy during another debate, saying that: “[T]here has been this difference between us over when and whether the president should offer a meeting, without preconditions, with those with whom we do not have diplomatic relations. And it should be part of a process, but I don’t think it should be offered at the beginning.”

The Clinton campaign touted in an email they sent out, “As Secretary of State, Hillary Clinton twisted a lot of arms to build a global coalition to impose crippling sanctions and apply unprecedented pressure on Iran. And she secretly sent senior aides to engage in back-channel diplomacy with Iran, ultimately bring them to the negotiating table and paving the way for the historic deal that blocks Iran’s pathways to a nuclear weapon.”