IMPEACH BUSH

FAYETTEVILLE, North Carolina (Reuters) - Democratic presidential candidate Barack Obama criticized Republican John McCain on Wednesday for misidentifying Iraqi extremists, saying he fails to understand the war has emboldened U.S. enemies.

On the fifth anniversary of the U.S.-led invasion of Iraq, the war took center stage on the U.S. campaign trail.

Obama attacked both McCain and his Democratic opponent, New York Sen. Hillary Clinton, as representing conventional thinking in Washington that needs to be changed in the November election. McCain and Clinton backed a 2002 resolution supporting U.S. military action against Iraq.

Clinton's campaign spokesman Phil Singer accused Obama of taking "practically no action to end the war until he started his White House run while Senator Clinton has been a consistent critic of Iraq for many years."

As a senator from Illinois, Obama has voted for imposing timetables for withdrawing U.S. troops from Iraq, a position Clinton also has been supporting.

And McCain's campaign said Obama was backing a risky strategy of pulling U.S. troops from Iraq that would leave the country vulnerable to civil war and genocide.

McCain, the 71-year-old Arizona senator who touts his national security experience as a main reason why he should be elected, gave Democrats a line of attack to use against him on Tuesday.

On a Middle East and Europe swing intended to bolster his national security credentials, McCain got tangled up in stating which Islamic extremist group in Iraq that neighboring Iran is accused of supporting.

At a news conference in Amman, McCain said Iran supported the Sunni group al Qaeda in Iraq, until he was corrected by a colleague. U.S. officials believe predominantly Shi'ite Iran has been backing Shi'ite extremists in Iraq, not al Qaeda in Iraq, a Sunni group.

It was the first stumble of note that McCain has made since clinching the Republican presidential nomination early this month, and Obama quickly pounced on it.

"Just yesterday, we heard Senator McCain confuse Sunni and Shi'ite, Iran and al Qaeda," Obama said.

"Maybe that is why he voted to go to war with a country that had no al Qaeda ties. Maybe that is why he completely fails to understand that the war in Iraq has done more to embolden America's enemies than any strategic choice that we have made in decades," the Illinois senator said.

McCain senior adviser Mark Salter said a U.S. pullout from Iraq would allow al Qaeda to claim victory and to pretend that this would not happen is "foolish supposition."

He added: "Iran, which trains Shi'ite extremists and is known to arm and equip Sunni extremists, a fact Sen. Obama is apparently unaware of, will also view our premature withdrawal as a victory."

Salter, in a telephone interview, said he based his statement that Iran had armed and equipped some Sunni extremists on a recent report by expert Frederick Kagan of the American Enterprise Institute.

Obama also mocked McCain's oft-stated vow to follow Osama bin Laden to "the gates of hell" if elected, arguing the U.S. focus should have been on Afghanistan and Pakistan instead of Iraq.

"We have a security gap when candidates say they will follow Osama bin Laden to the gates of hell but refuse to follow him where he actually goes," Obama said.

On a visit to Detroit, Clinton reiterated her position that the United States could start withdrawing troops within 60 days of her taking office, and she said it was up to the Iraqis to take responsibility for their country's future.

"We cannot win their civil war. There is no military solution," she said at a quickly arranged stop to push for a repeat of Michigan's presidential nominating contest, which had been disqualified because it violated party rules.

McCain, who strongly supported President George W. Bush's troop increase a year ago, said the United States and its allies "stand on the precipice of winning a major victory against radical Islamic extremism."

"The security gains over the past year have been dramatic and undeniable," McCain said.

And this time, he got the extremist identification correct.

"Al Qaeda and Shi'ite extremists -- with support from external powers such as Iran -- are on the run but not defeated," he said.

(Additional reporting by Jeff Mason and Andy Sullivan, writing by Steve Holland, editing by David Wiessler)

(To read more about the U.S. political campaign, visit Reuters "Tales from the Trail: 2008" online at http://blogs.reuters.com/trail08/)