Iraqi Parliament Speaker Osama al-Nujaifi, left, meets with Iranian President Mahmoud Ahmadinejad, right, October 2.

Story highlights

NEW: Most Iranian-backed militias in Iraq were active south of Baghdad

Iran may seek to take advantage of Iraq's vulnerabilities, analysts say

Obama administration says it's not worried about Iran in Iraq

But Sen. John McCain says the U.S. stand-down was Iran's top priority

CNN  — 

The announced withdrawal of U.S. troops from Iraq put new attention Friday on the influence of Iran, accused of supporting Iraqi militias that have killed American soldiers, but analysts were reluctant to declare the pullout a clear victory for Iran.

Still, President Obama’s announcement that all servicemen in Iraq will be home for New Year’s – ending a war that began in 2003 – could reveal weaknesses and vulnerabilities in Iraq, which could strengthen Iran’s hand, analysts said.

“It will not have negative effects against Iran,” James Gelvin, history professor at the University of California at Los Angeles and Middle East expert, said about the U.S. pullout.

But the relationship between Iran and Iraq’s Shias isn’t monolithic, especially if Iraq’s firebrand Shia cleric Muqtada al-Sadr seeks to reassert his own power, he said. Iran and Iraq have a Shia majority.

“There are tensions” between Iran and Iraq, Gelvin said. “We don’t know if this is going to be a replay of (the Iran-Iraq War of) 1980 to 1988 or if it’s going to be different. I think anyone giving you information on this is whistling in the wind.”

Mike Breen, vice president of the progressive Truman National Security Project in Washington, described the ties between Iran and Iraq as “complicated.”

“I would say it’s too soon to tell because the Iraqi people and the Iraqi government are only beginning to write the next chapter in their nation’s history, and they have a complicated relationship with their neighbor Iran, and that’s not always been a positive relationship,” Breen said.

On the one hand, Iran, one of the last theocracies and military regimes in the Middle East, is surrounded by the democratic uprisings of Arab Spring. But its immediate borders will no longer have to face the might of the U.S. military, analysts said.

“At the very least, what they get out of an American withdrawal of Iraq is an extraordinarily weak Iraq, and at most they get a manipulable Iraq,” Gelvin said.

“The American position in the region is weakening, which means that regional powers are going to exert themselves more. And the two most important regional powers right now are Turkey and Iran. Without the United States really there, people are going to be looking around and perhaps cutting deals,” Gelvin said.

But Denis McDonough, the president’s deputy national security adviser, contended that Iran is becoming more isolated in the eyes of the international community – as well as weaker economically. He cited the international criticism against Iran’s human rights record and nuclear program.

“Am I afraid about the Iranians?” McDonough told CNN. “The answer is no.”

Republican Sen. John McCain of Arizona differed and said he was concerned about the U.S. pullout – and how it works to Iran’s advantage.

“We’re leaving Iraq completely – which is the No. 1 priority of the Iranian(s),” McCain said. “We are taking unnecessary risks in Afghanistan by withdrawing troops there, and I can tell you from traveling the world, that in the world they believe the United States is withdrawing and is weakening. That’s a fact.”

A U.S. official who was not authorized to speak for attribution said the Iraqis “will not roll over” to Iran and added how the two nations have a long history of border disputes and fought the eight-year war from 1980 to 1988.

“The Iranians have been trying to gain influence in Iraq for some time and will continue to do so. It’s in Iran’s interest to have a relationship with a neighbor they’ve gone to war with in the past. At the end of the day, however, the Iraqi people will decide whether Iranian meddling is acceptable,” the official said.

“Iranian influence in Iraq has limits,” the official added. “The Iraqi people have a strong sense of nationalism and won’t take kindly to interference from a neighbor with whom it fought a bloody war.”

U.S. commanders, including Adm. Mike Mullen, the chairman of the U.S. Joint Chiefs of Staff, have blamed Shia Muslim militias backed by Iran for increased deadly attacks on American troops.

Last month, Major Gen. David G. Perkins, the commander of U.S. Division-North and the 4th Infantry Division, said that Iranian-backed attacks or militias have been active throughout Iraq.

“The majority of them historically have occurred in the south, in Baghdad,” Perkins said. “The areas where I see them up here in the north historically have been in Diyala province, because I kind of have a Sunni-Shia divide there. And at the beginning of the year, we were seeing Iranian-type munitions such as our explosively formed penetrators and things like that, which come across the border from Iran.

“Recently, there has been a reduction in the number of attacks that we attribute to Iranian-backed militias. But, again, we know that capacity is there, so we keep those pressures on those networks,” Perkins said.

CNN’s Pam Benson contributed to this report.