Israel and Saudi Arabia strongly opposed the recent agreement to limit Iran’s nuclear program, in part because they fear it will remake the Middle East to their detriment. It is up to Iran to prove them wrong, and that can start in Syria.

Iran’s leaders claim that if they were treated as a regional power rather than a pariah, they could act constructively. If they can’t demonstrate the truth of this claim, then the skeptics are probably right: In the midst of intensifying conflicts between Sunnis and Shiites, and between Iranian proxies and Israel, negotiated limits to Iran’s nuclear ambitions will always be at risk of unraveling.

Iran can make its case by helping deliver an agreement that ends the bloodshed and suffering in Syria, where its Revolutionary Guard and Hezbollah proxies are fighting for President Bashar al-Assad and his minority Alawite regime. By using its influence with Assad to secure a settlement, Iran would, at the least, quell fears that it might use part of the cash from sanctions relief to boost its war efforts abroad.

In announcing this week that the much-delayed Syrian peace talks will start Jan. 22, United Nations Secretary-General Ban Ki-Moon rightly wanted to use the momentum of the Iranian nuclear agreement to break the impasse. These talks should start small, much as the Iranian nuclear negotiations have done, putting aside at the start the hardest issues involving a political transition.