In three different crises now roiling the Middle East, all roads seem to lead to Tehran. In Iran, there's a nuclear standoff, with the government refusing to end its uranium-enrichment program. In Iraq, there is growing sectarian violence involving Shiite militias and parties with close ties to Iran. In Israel, there is open warfare against Islamic radicals who receive arms and funding from Iran.

Secretary of State Condoleezza Rice said last week, "Iran has been a principal funder and supporter of Hezbollah. There have been obvious numerous public contacts between the Iranian regime and Hezbollah and Hamas." Israelis agree. "The ideological support, the weapons, everything comes from Iran, and in the case of Hezbollah through Damascus," a senior Israeli official told The Washington Post.

Israelis believe that Hezbollah is trying to transfer its kidnapped Israeli soldiers to Iran. That's one reason Israel attacked Beirut's airport and cut off land and sea routes out of Lebanon. Israel also claims that Hezbollah rockets that hit Haifa were made in Iran and that Iran was involved in the missile strike that damaged an Israeli ship.

Why would Iran want to provoke this crisis? Some observers argue that Tehran is trying to divert attention from its nuclear program. "Iran definitely has some cards to play against America, and they are using Hezbollah and Hamas to that end, to shift the position on nuclear arms," Eyad Sarraj, a Palestinian human-rights activist, told The Post. Israeli analyst Meir Javedanfar said, Iran is "showing the West, by attacking the soft underbelly of Israeli security, that pushing it around will have consequences." Moreover, this Israeli-Palestinian crisis, unlike previous ones, was instigated by radical Islamists. That is why Iran sees an opportunity.

Since the Iraq war began, Iran has become a much more powerful player in the Middle East. As Shibley Telhami, senior fellow at the Brookings Institution, observed, "Iraq is not going to be a major power in any foreseeable future, no matter what happens militarily. So Iran is now the dominant power in the [Persian] Gulf." And one more thing: "The additional weight of oil, given how the oil market has moved, gives them tremendous clout."

Iran's influence in the Middle East has always been limited by the fact that Iranians are not Arabs. They are Persians and Shiites. Iran finds a natural ally in Hezbollah, a radical Arab Shiite group based in Lebanon. "The Iranians have nurtured Hezbollah and helped them put all those rockets in place in Lebanon," said Sen. John McCain, R-Ariz.

For years, Iranians have tried to assert their leadership of the Palestinian cause. "Since the revolution, Iran has highlighted the question of Palestine, particularly the question of Jerusalem, as a Muslim issue," Telhami said. "[Iran] has made it a way to project itself in the Arab and Muslim world."

That strategy may be working. "Iran is not a natural ally and certainly not a country Arabs have held as a model," Telhami said. "But it is finding resonance in this environment."

The strategy also holds risks for Iran. Hezbollah could end up defeated or weakened. Many Arab governments do not want this war. And they are likely to resent the roles played by Hamas, Hezbollah, and Iran in provoking it.

How much influence does the United States have? Over Hamas and Hezbollah, very little. The U.S. considers them terrorist organizations and will not deal with them. The U.S. does have influence with Lebanon and the Palestinian Authority, but neither of those governments seems to have control over the militant Islamists driving the crisis.

Iran and Syria are the two countries with the most influence over the militants, but the U.S. has limited contact with those governments. As a result, the U.S. has to rely on indirect and uncertain tools—international pressure and third-party diplomacy. The U.S. has real influence only with Israel; the Bush administration is urging restraint in an effort to minimize civilian casualties and avoid a full-scale regional war.

"The Bush administration was caught without a policy," Telhami said. And now it may be paying a price for what he calls "the reluctance of the administration to make Arab-Israeli issues a priority."