Regrettably, the Iranian response has been unreflective, pugnacious - and most important - un-Islamic.

A verse in the Quran states: "If they [the unbelievers] incline to peace, you should also incline to peace." Because believing Muslims revere the Quran as sacred scripture containing the very words of God, it is not unreasonable to expect that professed Muslims should take these words to heart.

Inclining to peace should manifest itself in a willingness to negotiate through diplomacy, especially when an adversary indicates a preference for it. When the pagan Meccans sought arbitration with the Prophet Muhammad and his followers in 628, he concluded the Treaty of Hudaybiyya with them. The treaty included provisions not entirely favorable to the Muslims, but the Prophet did not waver in his resolve to sign this agreement. Some of his companions grumbled about the unequal treatment of Muslims in this accord, and a few were even opposed to the whole idea of peacemaking.

The arguments were familiar - the Meccans had driven the Muslims out of their homes, looted their belongings, and persecuted them for their beliefs. As far as one could tell, the Meccans remained committed to destroying the nascent faith and its adherents. How could one sit down with such trenchant enemies, whose intentions were suspect? The Quran answers those objections in the very next verse: "And if they intend to deceive you - then surely God is sufficient for you." Scripture had made it clear that Muslims should take a risk for peace, and if the opposing side should desist from hostilities, Muslims should reciprocate in kind.

The treaty was signed and was meant to guarantee 10 years of peace. As it turned out, the worst fears of Muhammad's followers proved to be true. The Meccans soon violated the agreement and fighting loomed. Further negotiations, however, brought about the peaceful surrender of Mecca and a general amnesty for the previous enemies of the Muslims.

Muhammad and his immediate successors implemented a principle known as "the joining of hearts," according to which the erstwhile enemies of Islam were to become reconciled with Muslims through charity and inclusion within the new community. The fact that Muslims throughout time have not always implemented these principles in no way makes them less normative for contemporary Muslims.

Both Sunnis and Shiites read the same Quran, and both agree that its ideals were perfectly realized by their Prophet. Thus Iran, a predominantly Shiite nation, is just as obligated to follow Quranic teaching as any other Muslim-majority country with a commitment to Islamic principles.

After eight years of relentlessly hawkish U.S. policies toward the Middle East (and some would argue toward the Muslim world in general) under President George W. Bush, Mr. Obama has clearly set a new course. He has expressed resolute good will toward the majority of Muslims in the world who also desperately - and audaciously - hope for change for the better, as global surveys and polls have repeatedly shown.

Why, then, has Iran's supreme leader, Ayatollah Ali Khamenei, a religious man by all accounts, spurned Mr. Obama's outreach and rejected negotiations? He certainly cannot claim a scriptural imperative for his behavior.

From a realpolitik perspective, risking political capital for peace may appear to be a foolhardy venture, and Mr. Khamenei will certainly be criticized by Iran's hawks for talking to "the Great Satan."

But morally speaking, he and other Iranian leaders owe it to their people and to the world to sit down at the negotiating table in view of the fact that the Islamic Republic of Iran has been a principal actor in some of the major conflicts of our time.

It is not enough for Muslims to repeatedly affirm that Islam stands for peace; they need to demonstrate that Islam means peace. When valuable opportunities for peacemaking occur and it is Muslim leaders who fritter them away, they should expect scorn to be directed at them and at their hollow rhetoric.

In the popular American imagination, Muslims after 9/11 have become tarred by the brush of violence. Now we can add to this image an unholy lack of moral courage and intransigence in the face of a singular opportunity to put an end to a nuclear standoff that could engulf the whole world.