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President Bush warned on Tuesday that Iran is plotting to extend its "murderous" influence over Iraq and is threatening to destabilize the Middle East under a "shadow of a nuclear holocaust."

Iran, Bush said, "is the world's leading state sponsor of terrorism. Iran backs Hezbollah, who are trying to undermine the democratic government of Lebanon. Iran funds terrorist groups like Hamas and the Palestinian Islamic Jihad, which murder the innocent and target Israel and destabilize the Palestinian territories."

He also pointed to actions like the arrest of U.S. scholar Haleh Esfendiari and Iran's nuclear ambitions as destabilizing forces.

"Iran has arrested visiting American scholars who have committed no crimes and posed no threat to their regime. And Iran's active pursuit of technology that could lead to nuclear weapons threatens to put a region already known for instability and violence under the shadow of a nuclear holocaust," Bush said.

Speaking to an audience attending the 89th American Legion convention being held in Reno, Nev., Bush vowed to continue the fight against radicals through military action in Iraq but noted that this is a "short term" plan to be accompanied by a longer-term solution.

The president did not give definitions for such time frames, but said the United States and its allies are "keeping the pressure" on extremists by forcing them to move out of their safe havens, cutting off their financing and disrupting their networks.

"In the short term, we're using all elements of American power to protect the American people by taking the fight to the enemy. Our troops are carrying out operations day by day to bring the terrorists to justice," he said. "Our strategy is this: We will fight them over there so we do not have to face them in the United States of America."

Bush said long-term solutions for confronting terrorist groups and their state sponsors include "advancing freedom and liberty as the alternatives to the ideologies of hatred and repression," seeking to install secure, democratic states "that are at peace with one another, that are participating in the global markets and that are partners in this fight against the extremists and radicals" and drying up "the stream of recruits" for Al Qaeda and other terror networks.

Facing pressure from Democrats to begin withdrawing troops from Iraq, Bush has made several recent speeches in the run-up to a September report from his administration to show his plans to increase troops there are working.

That report, to be given to Congress by the top U.S. commander in Iraq, Gen. David Petraeus, and the top U.S. diplomat there, Ambassador Ryan Crocker, has become a major focal point in the debate on Capitol Hill over the success of the surge.

The administration, citing new successes, has been posturing itself to maintain current troop levels at least into the spring.

Bush said those who are ready to bail out of Iraq are being impatient and overly demanding.

"It's going to take time for the recent progress we have seen in security to translate into political progress. In short, it makes no sense to respond to military progress by claiming that we have failed because Iraq's parliament has yet to pass every law it said it would," he said.

"Leaders in Washington need to look for ways to help our Iraqi allies succeed, not excuses for abandoning them," the president added, saying the United States and its allies have little choice but to continue to support the nascent government in Iraq.

In his remarks, the president called Iran one of the faces of evil seeking to exploit religion and enslave the Middle East.

He declared that such evil is "not the true face of Islam" and warned that Iran, Al Qaeda or others who wish to impose virulent forms of radical Islam must be stopped from gaining a foothold in Iraq.

"We seek an Iran whose government is accountable to its people, instead of to leaders who promote terror and pursue the technology that could be used to develop nuclear weapons," he said.

The president offered a long list of offenses committed by Iran against its neighbors in the region, but suggested the United States is considering military options to confront Iran.

Among the many offenses cited were Iran's backing Hezbollah, its sending arms to the Taliban in Afghanistan, its funding Hamas and other Palestinian terror groups, arresting American scholars like Esfendiari and pursuing nuclear technology.

"Iran's actions threaten the security of nations everywhere," the president said. "And that is why the United States is rallying friends and allies around the world to isolate the regime, to impose economic sanctions. We will confront this danger before it is too late.

"I have authorized our military commanders in Iraq to confront Tehran's murderous activities," Bush said, adding that if Iran or Al Qaeda were allowed to gain control of Iraq, the Middle East would face serious instability.

Responding to the president's speech, Sen. Joe Biden, D-Del., a 2008 presidential candidate, said the only evident political progress in Iraq is from the bottom up.

Biden said his plan to split the country into three confederated states based on sectarian factions — Sunni, Shia and Kurd — is the best approach, and could involve Iran in negotiations.

"We should refocus our effort on making federalism work for all Iraqis. And what I would do — and what the president should be doing now — is initiating a diplomatic offensive, not a new surge offensive, to do just that: a diplomatic offensive, bringing in the United Nations, the major countries around the world, including Germany, and Iraq's neighbors, to help implement and oversee the political settlement I am proposing and what the Iraqi constitution calls for," he said.