As President Hassan Rouhani of Iran makes his debut appearance before the United Nations in New York this week, the world is exercised with anticipation about his remarks. Granted Mr. Rouhani’s words will surely not resemble the theatrics put on by his predecessor Mahmoud Ahmadinejad, performances that resulted in the U.S. and Israeli delegations walking out of the venue. No, expectations this time around are much higher for the Iranian President, perhaps too high.

Since his election, Rouhani has used the podium in Tehran to promote a contemporary relationship between Iran and the West. Whereas Ahmadinejad preferred anti-Semitic hyperbole and diplomatic posturing, President Rouhani has suggested over the past month that he sees a somewhat different path ahead for Iran. For Rouhani positive relations with the United States appear to be atop his agenda. Before we break out the champagne, however, there are some inconvenient truths that qualify this reality.

First, in Iranian politics Rouhani has little power. President Obama might be able to convert his rhetoric to political capital in order to pass legislation or create a groundswell for support in the United States. Mr. Rouhani does not have this capacity. He may be able to create that popular support over a particular issue in Iran, but even if this were to occur the ultimate power rests with the Ayatollah Khamenei. The Ayatollah is the final arbiter, plain and simple. Further, this is not news. The Ayatollah, after all, is known as the Supreme Leader. So while Rouhani’s rhetoric about improving relations between Iran and the United States may seem uplifting, it is crucial to remember that Khamenei is back in Iran pulling the strings.

Rouhani’s election to the Presidency was only a matter of grace from the Ayatollah, all things considered. If Khamenei had preferred, he could have easily chosen another candidate to assume the Presidency. The 2009 Election that was staged in Ahmadinejad’s favor, for instance, is just one example of how simply the Iranian people can be cheated out of a fair election. All we know for certain is that Khamenei, while holding the power to rig the 2013 Election, chose to let these results stand. Why the Ayatollah granted Rouhani the Presidency is mere speculation. Another absolute certainty in Tehran is the residence of power; in Khamenei, not Rouhani.

Second, actions speak louder than words. In recent interviews and statements, Mr. Rouhani has stated outright that Iran is not pursuing nuclear weaponry. At first glance, this seems like a major breakthrough. Yet, as these words are announced the centrifuges in Iran continue to spin. If Rouhani’s rhetoric is to be matched properly with a desired outcome, then Iran’s nuclear program must immediately become more transparent and, so far as weapons are concerned, halted. In reference to an earlier point, however, Rouhani cannot do much more than use rhetoric here.

If real change regarding nuclear weaponry is in the cards then it will come about after Khamenei has a change of heart. Until that time, the U.S. will only have pleasant rhetoric to go on. In fairness to Rouhani, it must be said, this rhetoric is at least an improvement on the vile speeches of his predecessor.

Nuclear weapons are admittedly abhorrent tools of total destruction, and the nonproliferation of such weapons should be the ultimate goal. But, these weapons are tremendously dangerous in the hands of messianic fundamentalists, a group to which the Iranian mullahs belong, and a group that Hassan Rouhani must placate. That nuclear weapons exist as a status quo duopoly is a shame, but there are indeed groups who wish to acquire such weapons for their deployment, if not their use as tools for blackmail. For this reason the U.S. should remain very skeptical about lofty rhetoric from Rouhani, who has limited power himself and has not reflected any demonstrable change in Iran.