Iran stands at the cusp of a new era in its relations with the West as newly installed President Hasan Rowhani heads to New York to address the U.N. General Assembly. Rowhani is sending extraordinary signals about the need for a diplomatic reset after years of conflict.

President Barack Obama should proceed, albeit with extreme caution, to exploit this potential opening. Lots of topics, such as Syria’s civil war, are up for discussion, but the core issue is Iran’s nuclear program, which the West contends is focused on developing a bomb. Iran has long denied such plans but has repeatedly failed to honor treaty commitments to permit international inspections and be transparent about its nuclear operations.

Bellicose threats from each side have only worsened tensions, particularly the talk of military action against Iran and calls by Rowhani’s controversial predecessor, Mahmoud Ahmadinejad, for Israel to be “wiped off the map.” The rhetoric removed almost all chances of a diplomatic breakthrough.

Since his election in June, Rowhani has managed to silence Iran’s hard-line conservatives for the time being while advancing a conciliatory message to the West. Gone are the pronouncements of Holocaust denial that earned pariah status for Ahmadinejad.

Last Thursday, Rowhani penned an op-ed column in the Washington Post calling for world leaders “to lead in turning threats into opportunities” and work together “to end the unhealthy rivalries and interferences that fuel violence and drive us apart.”

In an interview with NBC News, he was emphatic: “Under no circumstances would we seek any weapons of mass destruction, including nuclear weapons.”

Let’s not forget what prompted this change of tone. International sanctions, spearheaded by U.S. pressure, helped isolate Iran and deeply shook its economy. Iranians are tired of hardship and constant tension with the West. Iranian voters’ shift from Ahmadinejad’s extremism to the more soft-spoken tone of Rowhani reflects a popular desire to do whatever Iran must to get the sanctions eased.

A thaw is long overdue. Obama and Rowhani have exchanged letters. There’s even talk of arranging some sort of direct meeting between the two in New York. Any such encounter would be rich in symbolism, but what the world demands is substance in the way of full Iranian compliance with its international obligations.

There’s no harm in talking, and there’s little payoff at this point in deepening tensions with more bellicose pronouncements. But amid the cordiality, Obama should make clear that the sanctions relief Iran seeks will come only when Rowhani’s kind words are matched with earnest deeds.