Washington charged last week that Kawtharani had "taken over some of the political coordination of Iran-aligned paramilitary groups" formerly organised by Iranian Revolutionary Guard Corps commander Qasem Soleimani.

In fact, when a US drone strike in January killed Soleimani and others in a small convoy outside the Baghdad airport, the little-known but powerful official from Lebanon's Iran-backed Hezbollah movement was initially rumoured to have died alongside him.

It was quickly confirmed that Kawtharani, who has long spearheaded Hezbollah's Iraq policy, was not among those killed in the attack that brought arch enemies Tehran and Washington to the brink of war.

But rumours of his demise only proved his place among the shadowy pro-Iran brokers steering politics in Iraq, the oil-rich but poverty-stricken country torn by unrest since the 2003 US-led invasion that toppled dictator Saddam Hussein.

Keen to curb Iran's influence in Iraq, the United States last week announced the reward of up to $10 million for any details on Kawtharani's activities or associates.

The State Department accused him of inheriting part of Soleimani's role coordinating among pro-Tehran factions that have attacked foreign diplomatic missions and "engaged in wide-spread organised criminal activity".

- 'The conductor' -

Washington had first sanctioned Kawtharani as a "terrorist" in 2013 for providing "training, funding, political, and logistical support to Iraqi Shi'a insurgent groups".

Born in Iraq in the late 1950s, Kawtharani studied in the holy shrine city of Najaf and is married to an Iraqi woman with whom he has four children.

Little is known about his early political work, but his rise to prominence began following the US-led invasion.

"Kawtharani was appointed to head Hezbollah's Iraq file in 2003 and has reported directly to its secretary general, Hassan Nasrallah," said a source close to Hezbollah's senior ranks.

In that role, the slender sheikh travelled frequently between Baghdad and Beirut to negotiate with Iraqi figures, particularly during politically turbulent times like government formation and elections.

He was often in the Prime Minister's Guesthouse, an ornate resort in Baghdad hosting officials and foreign dignitaries, in his traditional white turban and black robe.

"In that role, he was like a copy of Soleimani," a senior Iraqi official who met with him several times told AFP, referring to the Iranian general's infamous shuttle diplomacy.

Kawtharani fluently speaks Iraqi dialect, which differs markedly from Lebanese Arabic.

"He's got a lot of experience and is the only foreigner, after Soleimani, to know the Iraqi political scene inside out," another Hezbollah source said.

Iraqi political expert Hisham al-Hashemi said Kawtharani wore multiple "hats".

"He's the conductor in the Shiite loyalist orchestra," said Hashemi, referring to the collection of Iraqi Shiite parties that see Iran's Supreme Leader Ali Khamenei as their main reference.

As such, he painstakingly builds consensus among Iraq's varying Shiite political and armed factions -- but he has also worked on bringing Iraq's Sunnis on board with their traditional Shiite rivals.

- A growing profile -

Following the US strike that killed Soleimani and top Iraqi commander Abu Mahdi al-Muhandis, Kawtharani saw his portfolio balloon further to include coordination with Kurdish parties.

"He became responsible for all the political factions," said Hashemi.

At the same time, he crafted ties between Iraq and Lebanon, where Hezbollah has strained under financial pressure from US sanctions.

"Kawtharani held sway over Iraqi politicians -- so much so that he asked for millions of dollars from Iraq last year to solve Lebanon's financial crisis," a diplomatic source told AFP.

The request was made outside the formal state-to-state channels and it was unclear if it was ever processed.

And while a second Iraqi official confirmed Kawtharani made the request, a source close to the sheikh in Beirut denied the overture.

The US's renewed spotlight on Kawtharani was worrying, another source close to him said.

"Seeking information about him now may be an introduction to a possible attempt at his arrest, or his assassination," the source said.

When approached by AFP regarding Kawtharani, numerous Iraqi and Lebanese sources declined to comment on his activities, hinting at fears their information would be used by the US to target him.

Given the backlash the US faced internationally following its assassination of Soleimani and Muhandis -- both key officials in their respective countries -- the US may target someone with a relatively lower profile.

"Assassinating the new Quds Force chief Ismail Qaani isn't among Washington's options right now. That's why they turned to Kawtharani. He's a party official but not a government one," the source said.