BEIRUT/MOSCOW (Reuters) - A senior Iranian official said on Thursday he hoped the Syrian government and its allies would drive U.S. troops from eastern Syria, challenging U.S. President Donald Trump as he weighs action in Syria over a suspected chemical attack.

A man walks with his bicycle at a damaged site in the besieged town of Douma, Eastern Ghouta, in Damascus, Syria March 30, 2018. REUTERS/Bassam Khabieh

Ali Akbar Velayati, top adviser to Iranian Supreme Leader Ayatollah Ali Khamenei, also said he hoped the city of Idlib in northwestern Syria would be recaptured from rebels very soon as he hailed a government victory in the eastern Ghouta.

He was speaking in a televised news conference from Damascus after Russian media reported that the Syrian government flag had been raised over Douma, which had been the last rebel pocket in the eastern Ghouta region.

The alleged poison gas attack took place in Douma on April 7, hours before the town’s last rebels surrendered. Assad and Russia have called reports of the attack bogus.

Velayati’s comments, coming after a major victory for Damascus which Assad has said is the reason for Western threats, threw down the gauntlet to Trump, who recently said he wanted U.S. troops out of Syria relatively soon.

Iran and Russia, Syrian President Bashar al-Assad’s two biggest allies, have sworn they will stand with Damascus in the face of possible Western military action.

“Idlib is an important Syrian city, and we hope it will be liberated very soon with the determination of Syria and its fighters. East of the Euphrates (river) is also a very important area. And we also hope big and important steps will be taken in order to liberate this area and expel the occupying Americans,” Velayati said.

Russian news agencies reported earlier on Thursday that the Syrian government had retaken full control of Douma as insurgents there withdrew, and that Russian military police were deploying in the town.

Eastern Ghouta had been the largest rebel redoubt near the capital Damascus. The government offensive to recapture eastern Ghouta began in February and killed around 1,700 people.

“The raised state flag over a building in the town of Douma has heralded (government) control over this location and therefore over the whole of eastern Ghouta,” Major-General Yuri Yevtushenko, head of the Russian Peace and Reconciliation Centre in Syria, was quoted as saying by Russian news agencies.

EVACUATION

The Jaish al-Islam group in Douma agreed on Sunday to withdraw, hours after the suspected chemical weapons attack.

Around 40,000 people, including thousands of rebels and their families, are leaving Douma for opposition areas in northern Syria under the surrender deal.

A commander in the military alliance backing Assad said Jaish al-Islam’s main leader in Douma, Issam al-Boudani, had departed in an evacuation convoy on Thursday.

“It should be finished today,” the commander said, referring to the evacuation.

However, a local Jaish al-Islam official reached inside Douma said the evacuation could take longer as large numbers of people had attempted to leave rather than come back under Assad’s rule.

“The batches are still going out. The number is not under control. It’s possible two or three (more) days,” he said.

Seven vehicles with Russian flags and military police markings stood near the crossing, as well as Syrian police, and two full buses drove through towards an assembly point before the convoy would head north, a Reuters witness said.

Meanwhile, the pro-opposition Orient TV broadcast footage of an earlier convoy arriving in al-Bab, a town in northern Syria controlled by Turkish-backed rebel groups. Men stood around, some with rifles over their shoulders, as buses arrived.

On Wednesday, Velayati toured eastern Ghouta and pledged to stand by Syria in the face of “any foreign aggression”.

Trump has said American missiles “will be coming” to Syria and described Assad as “a gas killing animal”, but on Twitter on Thursday he said possible military strikes “could be very soon or not so soon at all”.

Both Syria and Russia have said reports of the chemical attack were fabricated by rebels and rescue workers in the town and have accused the United States of seeking to use it as a pretext to attack the government.