BAGHDAD (AP) — With the Islamic State group driven from nearly all of Iraq, U.S. officials have suggested that the thousands of mainly Shiite paramilitary fighters who mobilized against the Sunni extremists three years ago lay down their arms.

But Abu Mahdi al-Muhandis, who once battled U.S. troops and is now the deputy head of the state-sanctioned Popular Mobilization Forces, says they are here to stay.

"The future of the (PMF) is to defend Iraq," he told The Associated Press in his first extensive interview with a Western media outlet. "The Iraqi army and Iraqi police say they cannot operate without the support of the Hashd," he added, using a shortened Arabic term for the paramilitary force.

In the years after the 2003 U.S.-led invasion, al-Muhandis led the Hezbollah Brigades, a feared Shiite militia with close ties to Iran and the Lebanese militant group of the same name. His real name is Jamal Jaafar Ibrahim, but he's still better known by his nom de guerre, and his rise to the top ranks of Iraq's security apparatus reflects the long, slow decline of U.S. influence over the country.

He participated in the bombing of Western embassies in Kuwait and the attempted assassination of that country's emir in the early 1980s, for which he was convicted in absentia and added to the U.S. list of designated terrorists. But like many Shiite militants, he returned to Iraq after the 2003 U.S.-led invasion. Two years later, he was even elected to parliament, before being forced to step down under American pressure.

In 2009, the State Department linked him to the elite Quds Force of Iran's Revolutionary Guard, calling him a "threat to stability" in Iraq, and as recently as last week it referred to him as a terrorist.

But in the summer of 2014, when the Islamic State group swept across northern Iraq, and the U.S.-trained and funded army collapsed, his and other Shiite militias mobilized in defense, halting the extremists on the outskirts of the capital. The mostly Iran-backed militias remained separate from the U.S.-led coalition, but over the next three years they helped Iraq's reconstituted military to drive IS out of most of the country.

Today, al-Muhandis, in his mid-60s, is among the most powerful men in Iraq, splitting his time between the front lines, Iran and his home and office in Baghdad's heavily-guarded Green Zone. He describes the PMF as a "parallel military" that will help keep the peace once IS is gone.

Al-Muhandis "demonstrates that Iran has a direct venue with which to influence Iraqi politics, and a powerful one at that," said Phillip Smyth, an expert on Shiite militias at the Washington Institute for Near East Policy.

"It's no secret," al-Muhandis said of his close relationship with Iran, the country where he spent decades in exile and underwent military training. He said he personally seeks spiritual and moral guidance from the country's leadership, but that the PMF only gets material support from Tehran.

Earlier this month, U.S. Secretary of State Rex Tillerson demanded that Iran-backed militiamen in Iraq return to their homes, integrate into the Iraqi army or leave the country.

Al-Muhandis casually dismissed the appeal. "Tillerson is asleep," he said.

"Iran was the only country that supported Iraq from the beginning of the Daesh crisis," he said, referring to the IS blitz in 2014. "It's like when you're in a hospital and you need blood. The Americans would be the one who would show up with the transfusion when it was too late."

As to whether the Americans should remain in Iraq, Al-Muhandis said: "We follow the Iraqi government despite our personal opinions, and our personal opinions are well known, so I won't repeat them here."

The PMF sprang into action again earlier this month, when federal forces retook the northern city of Kirkuk and other disputed areas from Kurdish forces in response to the Kurds' vote for independence in September. The military action, which caused few casualties and was celebrated as a victory by the country's Arab majority, gave a further boost to the paramilitary forces.

"What happened in Kirkuk is a success for the Iraqi government and the Iraqi forces," Al-Muhandis said, adding that his forces had helped coordinate the Kurdish withdrawal to minimize clashes and casualties. "We want a brotherhood with the Kurds," he said, referring to their shared struggle against Saddam Hussein in the 1980s.

The fighting nevertheless displaced thousands of people, according to the United Nations and Amnesty International, which documented the looting and destruction of "hundreds" of properties near Kirkuk.

International rights groups alleged widespread violations by the militias throughout the campaign against IS and said the government had failed to hold them accountable. Al-Muhandis and other commanders say any abuses were isolated incidents, and that perpetrators have been brought to justice.

Al-Muhandis rarely speaks to reporters, but his image is pervasive on social media, where he can be seen wearing olive fatigues and surveying front-line positions from Iraq's northern border to the western Anbar province, where troops and militiamen are battling IS in the last pocket under its control. He's often standing beside Gen. Qassem Soleimani, the head of Iran's elite Quds Force, and a key adviser to the PMF. Music videos shared online praise al-Muhandis' humility and fearlessness.

He can also be seen in photos attending strategy meetings chaired by Iraqi Prime Minister Haider al-Abadi. The PMF are officially an "independent military formation" under the prime minister's command.

Al-Muhandis holds a "pivotal" position in Iraq's political and security hierarchy, said Nathaniel Rabkin, managing editor of Inside Iraqi Politics, a political risk assessment newsletter.

"It's a source of concern in and outside Iraq," Rabkin said. "If you have elements of the armed forces or the security forces loyal to a particular political party you're creating a setup where it will be very difficult to have free, fair and competitive elections that don't descend into violence."

Iraq is set to hold parliamentary elections next year. When asked if his forces would participate in politics, al-Muhandis laughed, saying: "Don't mention it or you'll scare off all the politicians." He added that PMF fighters would be free to run for office, but must first leave the paramilitary organization.

Smyth, the militia researcher, doubts such rules would be enforced, noting the long history of militia commanders cycling in and out of political office.

Whether they run or not, Al-Muhandis said the PMF are "the biggest force that can influence the upcoming elections."