SHARM EL-SHEIKH, Egypt — As he toured the Middle East over the past five days, President Bush tried to shore up support for his strategy of isolating Iran in meetings with the leaders of Israel, Saudi Arabia, Jordan, Egypt, and the Palestinian territories. But the one session that did not take place laid bare the problems his administration faces as it tries to persuade its allies to keep the faith.

Mr. Bush was supposed to meet with Prime Minister Siniora of Lebanon yesterday. But Mr. Siniora had to cancel to deal with a political crisis at home that has highlighted the commanding position the Shiite movement Hezbollah, an ally of Iran, has assumed in Lebanon.

With Iranian-backed Hamas consolidating control in Gaza and Iranian-backed terrorists making trouble for the American-backed government in Iraq, Iran and its proxies appear to be on the march, and American allies are concerned that the Bush administration does not have an effective plan for coping. One Arab diplomat said Iran is on an unchecked “rampage.”

“Everyone is focusing on the Iranian nuclear bomb, which doesn’t exist, but in the meantime the Iranians are winning the souls of the people,” a former senior Israeli diplomat, Alon Liel, said. “They are winning the battle in Lebanon, and they are winning the battle in Palestine through Hamas.”

Speaking to reporters traveling with Mr. Bush yesterday, national security adviser Stephen Hadley acknowledged a certain “tactical success” by Iran in Lebanon, where Hezbollah defeated government-allied militiamen last week and made clear it is the most powerful force in the country. But he argued that the move could turn out to be a “strategic failure” by undermining Lebanese public confidence in Hezbollah because it used its terrorists to fight government-allied forces.

Mr. Hadley said he sees “an opportunity for the Lebanese forces of democracy and freedom, and for those in the region that support it, to hold Hezbollah to account and hopefully to clip its wings a little bit. We will have to see. This is a story very much in progress.”

Mr. Bush, in a speech yesterday at the World Economic Forum here, criticized both Iran and Syria, which also backs Hezbollah, and singled out Iran for what he believes are its efforts to obtain a nuclear bomb.

“Every peaceful nation in the region has an interest in stopping these nations from supporting terrorism,” Mr. Bush said. “And every peaceful nation in the region has an interest in opposing Iran’s nuclear weapons ambitions. To allow the world’s leading sponsor of terror to gain the world’s deadliest weapon would be an unforgivable betrayal of future generations.”

Mr. Bush described the two countries as among the “spoilers who stand in the way” of positive reform in the Middle East.