The Western world knows Mahmoud Ahmadinejad the rabble-rouser, the Holocaust denier and the election-rigger. The Iranian president did nothing to dispel this image during his United Nations speech last week, with his anti-Semitic allusions and rambling indictment of capitalism.

As the U.S. and other leading powers prepare to sit at the negotiating table with Iran this week, they'll come to know another version of Ahmadinejad — a leader propelled by weakness at home, who will say he is willing to talk but may offer only tantalizing, unconvincing proposals.

For the Obama administration, which has made engaging with adversarial states a principle of its foreign policy, one of the biggest challenges will not be a belligerent Iran, but a disingenuous one.

The urgency of dealing with Iran's nuclear program has only intensified with the recent revelation that Tehran was constructing yet another clandestine facility. Even so, Washington's dilemma remains the same: how to maintain a united international front while avoiding being trapped in inconclusive talks.

Ahmadinejad is savvy enough to recognize that his fraudulent election has eroded not just the Islamic republic's legitimacy but his own standing in Iran and in the larger Muslim community. Ahmadinejad emphasizes his so-called electoral triumph and the significance of the election in Iran's allegedly unfolding democracy.

To reclaim his lost luster, he will be tempted to reach out to the Western powers, searching abroad for the validation that he is so lacking at home. At this week's talks, Iran's representatives are likely to subtly hint of cooperation to come — but only if the talks continue. However, such gestures do not mean Iran is prepared to offer meaningful concessions and impose any restraints on its nuclear ambitions. Ahmadinejad, who has fused the nuclear program with Iranian nationalism and criticized reformers for being too accommodating to Western demands, will have a tough time compromising on the nuclear front.

Ahmadinejad has presented a quandary for an Obama administration committed to a diplomatic solution on Iran — a quandary only aggravated by the Iranian leader's sham election and the ensuing crackdown on political opponents. During Iran's turbulent summer, I served as an Iran adviser in the State Department, and I saw the challenge of criticizing that country's electoral fraud while preventing the United States from being a pawn in its internal debate.

Having made reduction of the nuclear danger and arms control one of the central pillars of its foreign policy, the administration could not stand by and witness Iran's expanding array of centrifuges.

Now, although the imperative of engagement remains, the challenge for the United States is not just to deny Ahmadinejad a platform for his self-aggrandizement but also to deal with the full sweep of the Iran problem. Given the Islamic republic's bogus election, abuse of its citizens and continued sponsorship of international terrorism, the canvass of any negotiations must go far beyond Iran's nuclear ambitions. Ironically, Tehran has come to Washington's rescue, stipulating in its own proposal that it stands ready to "embark on comprehensive, all-encompassing and constructive negotiations."

A model for negotiating with Iran can be found in the annals of Cold War diplomacy: the Helsinki Accords of 1975. The Soviet Union — which had amassed as many nuclear weapons as the United States and was even more sensitive to criticisms of its internal order than Iran — agreed to discuss individual rights and regional affairs in exchange for Western recognition of its sphere of influence in Eastern Europe.

The U.S. should insist on discussing several issues: the nuclear program, of course, but also Iran's sponsorship of terrorism, its interference in the affairs of its neighbors and human rights. It is hard to see how Ahmadinejad could use such talks to relegitimize his tainted rule.

U.S. insistence on discussing the full array of Iranian malfeasances has the extra advantage of determining whether Tehran's proposal for comprehensive dialogue is real. If Iran is truly interested in escaping its pariah status, then it will swallow the bitter pill of such discussions. Conversely, if Ahmadinejad sees the negotiations only as a means of rejuvenating his image at home, he will probably reject such an agenda.

The notion that we cannot marry strategic concerns with moral values is belied by America's Cold War experiences. Ahmadinejad should not be afforded the luxury of international forums and dialogue with the great powers without being held accountable for his country's flawed electoral processes and its entanglements in terrorism, as well as its nuclear violations.

Ray Takeyh, a former senior adviser to the Obama administration on Iran, is a senior fellow at the Council on Foreign Relations. He wrote this commentary for The Washington Post.