Israeli Prime Minister Benjamin Netanyahu and Iranian President Mahmoud Ahmadinejad may seem very different, but they are united in their apocalyptic religious visions. Their respective beliefs may be propelling them on a collision course with potentially horrific consequences.

A pair of more disparate twins hasn't existed since the muscle-bound Arnold Schwarzenegger and the sharp-tongued, diminutive Danny DeVito played twins in the Hollywood movie of that name. One, the Israeli, is tall and thickset and often wears tailored suits. He is a gifted speaker and a militant anti-Iranian. The other, the Iranian, is short and slight and is almost always seen wearing an ordinary-looking beige windbreaker. He tends to be somewhat gauche and is a rabble-rousing populist and a self-declared enemy of Israel. The two men couldn't be more different.

But Israeli Prime Minister Benjamin Netanyahu, 59, and Iranian President Mahmoud Ahmadinejad, 52, are twins in spirit, which is not to imply in any way that they are morally equivalent. Both men are convinced of the absolute validity of their beliefs, both are obsessed by what they see as their higher calling, and both are convinced that theirs is a Messianic mission - a mission to "honor" a religion or "save" a people.

There is every indication that the coming nuclear negotiations between Washington and Tehran - if, indeed, they begin in the next few months with Ahmadinejad still Iranian president - will end in a stalemate by the end of the year. If that happens, U.S. President Barack Obama will push for tougher sanctions against Tehran in early 2010, with the reluctant support of the Russians and Chinese. The leadership in Tehran will interpret this as an aggressive act and will likely speed up its uranium enrichment, meaning that Iran will only be a few months away from having the capability to build a nuclear bomb. At some point next spring, things could have proceeded so far that the Israelis could decide, even without Washington's approval, to launch attacks against Iranian nuclear facilities. The entire Middle East would see thousands of casualties, and the consequences for the global economy would be devastating.