UN Secretary General Ban Ki-moon apparently hasn’t made a final decision about whether he will participate in the upcoming summit of the Non-Aligned Movement, which is scheduled to convene in Tehran early next week. If that is the case, here are two good reasons for him not to go:

1) His visit would undermine the international campaign against Iran’s nuclear drive and legitimize an odious regime that in the past few days has repeatedly called for the elimination of a United Nations member state; and

2) His visit would bolster Prime Minister Benjamin Netanyahu’s contention that sanctions and diplomacy have failed, and that the time for harsher measures has arrived.

Even if Ban ultimately decides to stay away from Tehran, the NAM summit may very well mark a watershed event in the ongoing standoff between the West and the Iranian regime. The attendance of thousands of high-ranking delegates, including dozens of world leaders, at a conference chaired by Iranian President Mahmoud Ahmadinejad, is destined to belie any possible claim that the campaign to isolate Iran is succeeding. It will not only embarrass the Obama Administration in Washington and undercut its policy of sanctions and diplomacy, but would also confirm two longstanding Israeli dogmas: that “the whole world is against us” and that in the effort to thwart Tehran’s designs “we can rely only on ourselves.” The summit is thus likely to shorten the path to war, psychologically at the very least.

Unfortunately, officials in Washington and Jerusalem, as well as top American Jewish leaders, were slow to wake up to the clear and present danger posed by the Tehran summit. A concerted campaign should have been launched many months ago to try and prevent world leaders from attending the conference. Now, officials in both capitals are belatedly scrambling to shut the door after most of the horses have bolted, focusing their efforts on Ban, whose attendance, more than that of any of the other important leaders going to Tehran, would symbolize international endorsement of the Iranian regime.

One can empathize with Ban’s predicament. The Non-Aligned Movement represents more than 120 countries, and constitutes the biggest voting bloc in the United Nations. Many of these countries are either sworn enemies or at least deeply suspicious of the United States and Israel, and support Iran’s nuclear ambitions. Just like any other politician, Ban would need a particularly persuasive reason to cross such a significant part of his constituency.

But Iran’s leadership easily surpasses such a threshold and provides compelling arguments against Ban’s participation. It is hell bent on acquiring nuclear weapons, it has repeatedly deflected and defied UN Security Council resolutions and it has consistently called for the elimination of Israel, with both Supreme Leader Ali Khamenei and Ahmadinejad calling it a “cancerous tumor” that “will be removed.” The fact that they have done so in the past few days, with full awareness of the upcoming high-profile summit, should be proof enough of their malevolent intentions.

According to press reports, Ban harbors hopes that his visit will achieve some sort of diplomatic breakthrough. It is hard to understand what these commendable aspirations are based on and why the Iranians would voluntarily surrender to Ban what they have adamantly refused to relinquish, despite crushing international sanctions. Much more likely is the scenario in which Ban helps the Iranians score a public relations coup that only emboldens them to continue with their race to achieve a nuclear bomb.

At the same time, Ban’s presence in Tehran might also go a long way to convince the Israeli public to give up any remaining hope that the world will somehow convince Iran to change its ways. The hitherto reluctant Israeli public opinion will thus be more inclined to support the Israeli hawks who claim that time for diplomacy is over and that the “Guns of August” – or September or October – should do the talking from now on. Decision makers in Washington, in turn, might come under greater pressure, for both substantive and political reasons, to escalate the U.S. campaign against Iran.

The bottom line is that Ban should stay home, because his participation in the NAM summit is a mistake - morally, strategically and personally as well. He does not want to go down in history as one more world leader who naively thought that he could extract last-minute concessions from evil dictators hell-bent on defying the world. In any case, if I were Ban’s media adviser, I would warn him against uttering the words “peace in our time” and tell him that whatever happens, he shouldn’t dare sport an umbrella when he returns from Tehran to New York, even if it rains.

Follow Chemi Shalev on Twitter @ChemiShalev