After being endorsed by Supreme Leader Ayatollah Ali Khamenei a day earlier, Hassan Rouhani was formally inaugurated by Iran’s Majlis on Sunday as the country’s new president. With Khamenei watching on stage, the reigns of the presidency were officially handed over by Mahmoud Ahmadinejad in a symbolic gesture.

Even before surprising international observers with a resounding win over his reactionary opponents in the June presidential election, Rouhani was a recognizable and highly respected individual in the Islamic republic’s political system. A man with considerable religious credentials, Rouhani managed his country’s National Security Council for sixteen years during the presidencies of Hashemi Rafsanjani and Mohammad Khatami. His stewardship of the council occurred at a time when Tehran was slowly trying to improve its public image after a long and bloody war with Iraq and later during a period when American soldiers were miles from Iran’s eastern and western borders.

But it was his brief tenure as Tehran’s chief nuclear negotiator with European powers between 2003 and 2005 that came to define Rouhani’s career so far. During his stint as the lead negotiator, Iran agreed to suspend uranium enrichment temporarily in order to stop a referral of its bad behavior to the United Nations Security Council — an action that would have resulted in a round of economic sanctions. Iran also agreed to allow officials from the International Atomic Energy Agency to probe its nuclear work more deeply.

Since then, the relationship between Iran and world powers over the nuclear issue has only worsened. No agreements have been signed since Rouhani’s initiative in 2003. In a sharp rebuke from Iranian hardliners to Rouhani’s concessions, Ahmadinejad overturned the accord upon entering office and resumed uranium enrichment activity.

With the election and swearing in of Rouhani, national-security officials in Europe and the United States are sincerely hoping that the former top negotiator will continue where he left off by opening up Iran’s nuclear facilities for inspection and providing documents and access that the IAEA has been seeking for years. Although Rouhani is faced with a slate of difficult problems, including a vastly underperforming economy tied down by a multilayered and comprehensive set of economic sanctions, cooling tensions with the West will be the first significant step in loosening the restrictions that have hamstrung Iran’s growth potential.

Moderation and respect have been two words that Rouhani has used to describe how he will govern as a future president. He expanded upon both of those themes in a speech before parliament. “I say candidly that if you [the West] want a proper response,” he said, “speak to Iran not with the language of sanctions but with the language of respect.”

The question is how the United States will respond to these words and whether the Obama Administration will be able to convince critics in Congress and elsewhere that another try at diplomacy is worth the time and effort.

A statement from the White House congratulating the Iranian people on exercising their democratic rights and said President Barack Obama was ready to sit down with the new Iranian government if it engages “substantively and seriously,” on the nuclear issue — a clear hint that the United States are willing to give diplomacy another opening.

Rouhani’s new team may be interested in talking directly with American officials, a development that would be controversial in some quarters but a welcoming change from the saber rattling that has come to define the bilateral relationship since the Iranian revolution in 1979.