At the same time Secretary of State John Kerry is warning that terrorists are fueling unrest across Iraq and Syria, he is now reaching out to a country his own department for decades has singled out as one of the prime sponsors of terrorism.

On Sunday, Kerry suggested that Iran could play a role in Syria peace talks, either formally or informally. The comments, though, have riled groups in the United States concerned about Tehran's long track record of propping up the Assad regime and fomenting chaos in the region.

Iran this month marks its 30th year on the State Department's list of State Sponsors of Terrorism -- while Syria has been on that list longer than any other.

"You have a forest fire that's raging and you're calling in some of the arsonists ... to discuss the best way to put it out," said Rabbi Abraham Cooper, associate dean of the Simon Wiesenthal Center, a Jewish human rights group. "It's mind-numbing."

Kerry suggests Iran might be able to play a productive role in Syria, given its close ties to the Assad regime. But at the same time, he used remarks Sunday to lament the "instability" in the region, responding specifically to Al Qaeda-tied fighters making gains in Iraq and Syria. Iran, though, has fueled the fighting by backing Assad and Hezbollah.

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    Sawsan Jabri, spokeswoman for the anti-Assad, U.S.-based Syrian Expatriates Organization, cited Iran's continued support of the Syrian government "with weaponry and fighters" in questioning Kerry's comments.

    "We believe its [stance] would be biased and its participation wouldn't add any positivity toward peace resolution," Jabri told FoxNews.com in an email.

    Cooper said Iran's involvement would make Bashar Assad "the happiest person in the room."

    "It's Iranians who kept Assad in his seat and still breathing through Hezbollah and other means," he told FoxNews.com. "If they're coming in, they've got Assad's back."

    The Iranian government has been one of the Assad regime's biggest benefactors during the three-year civil war. But the Obama administration on Sunday opened the door to Iranian involvement in upcoming peace talks for the first time.

    Speaking in Jerusalem, Kerry said the country "could participate very easily" if they accept the premise that the Assad regime must be replaced by a transitional government. "If Iran doesn't support that, it's very difficult to see how they're going to be 'a ministerial partner' in the process," Kerry said.

    However, Kerry indicated Iran could nevertheless have an informal role without taking that step.

    "Now, could they contribute from the sidelines? Are there ways for them conceivably to weigh in? Can their mission that is already in Geneva be there in order to help the process?" Kerry said. "It may be that there are ways that that could happen. But that has to be determined by the secretary general and it has to be determined by Iranian intentions themselves."

    The comments were the latest signal that the Obama administration is easing off its stance on Iran, weeks after striking a short-term agreement on Tehran's nuclear program. Negotiators are still trying to iron out the details of a more lasting agreement -- meanwhile, the administration is fighting to prevent Congress from passing a new sanctions bill which officials claim could derail nuclear talks.

    Cooper warned that if Iran gets more involved in peace talks, it could give them a key "piece of leverage" in nuclear negotiations.

    U.S. officials reportedly said Monday that it was "less likely than likely" that Iran would play a role in Geneva, and that the two nations have not directly discussed the possibility. At the same time, officials suggested Iran could improve its chances by getting Damascus to stop bombarding civilians in Aleppo, according to Reuters.

    France had been aligned with the United States in arguing that Iran should not participate in peace talks without accepting that Assad should go. The Syrian opposition also had opposed their involvement.

    On the other side, Russia has pushed for Iran's inclusion in the peace talks. And Iranian Foreign Minister Mohammad Javad Zarif said this fall that his country should be invited to the Geneva, Switzerland, talks and that leaders want to help in the effort to get chemical weapons out of Syria.

    The upcoming talks, which start Jan. 22, mark the second round of negotiations in Geneva.

    At this point, well over 100,000 people have been killed in the fighting, which many fear is fueling the rising violence in next-door Iraq.

    The Syrian opposition, aside from fighting the Assad regime, is increasingly fractured, with Islamist militant groups vying for power.

    FoxNews.com's Judson Berger contributed to this report.