Iraq could send troops into neighbouring Syria, Prime Minister Adel Abdul Mahdi said, days after the United States said it would withdraw from the war-torn country.
Iraq was "considering all its options" to defend itself from threats across its borders, the premier told a press conference on Monday.
Baghdad has already reinforced its Syrian border to defend against remaining ISIS pockets in the Euphrates River valley.
Iraq remains concerned that ISIS could expand its footprint in the war zone, Mr Abdul Mahdi said. He also expressed concerns that a fresh wave of Syrian refugees is being displaced into Iraq.
Last week, US President Donald Trump announced a total withdrawal of US troops from Syria, declaring that Washington had succeeded in defeating ISIS and were no longer needed.
The announcement drew criticism from allies such as France and Britain who say the insurgents have not been fully beaten.
Despite the American withdrawal from Syria, the US remains committed to fighting ISIS in Iraq and other areas, US Secretary of State Mike Pompeo told Mr Abdul Madhi on the phone on Saturday.
Mr Abdul Mahdi said his government has not received a US request to move troops inside Syria, but said the possibility was "circulating".
"Iraq will take its decisions in consultation with its friends and neighbours," he said.
Iraq does not have formal military forces inside Syria. But Iranian-funded and trained militias, part of the Popular Mobilisation Forces, are fighting along the Syrian border. The PMF are part of Iraq's national security apparatus, but have autonomy in their operations.
The influx of Iranian-backed paramilitaries into Syria from Iraq would bolster the Syrian government’s combat power as it moves to drive ISIS militants out of their last toehold in the country.
Syrian troops on Saturday sent reinforcements to the eastern province of Deir Ezzor close to an enclave controlled by ISIS and along the front with US-backed Kurdish-led fighters.
The government sent thousands of its elite forces to the western banks of the Euphrates River, mostly in the towns of Mayadeen and Boukamal. The troops brought to the area include members of the Tiger Force, an elite unit that defeated rebels and ISIS militants on several fronts over the past two years.
Analysts fear that the US withdrawal from Syria could leave the Kurdish-led Syrian Democratic Forces (SDF) fighting ISIS alone and exposed to military action by Turkey, which says the group is linked to the outlawed Kurdistan Workers' Party.
Kurdish forces in Syria are currently in talks with Russia, which is widely seen as the only actor capable of protecting the SDF from a Turkish assault.
After Mr Trump's announcement last week, SDF officials warned they would divert forces from the battle against ISIS to defend against Turkey, which is amassing forces along its border.
Turkey said on Tuesday it is working with the US to coordinate the withdrawal of American forces but remains "determined" to clear US-allied Kurdish fighters from northeastern Syria.
Foreign Minister Mevlut Cavusoglu told reporters that "if Turkey says it will enter, it will," in comments carried by private DHA news agency.
Speaking to reporters in Ankara, Turkish President Recep Tayyip Erdogan announced that a delegation was heading to Moscow and that he would meet with Russian President Vladimir Putin.
Meanwhile, the SDF made fresh gains against ISIS in their eastern Syrian stronghold on Monday, forcing hundreds of people to flee, the Syrian Observatory for Human Rights, a war monitor said.
SDF fighters are closing in on the villages of Al Shaafa and Sousa, where a few hundred holdout ISIS fighters are defending their last pocket in the Euphrates River valley, what is left of the group's self-proclaimed "caliphate", which once covered territory the size of Britain.
"The latest developments are in favour of the SDF and it appears that ISIS may collapse soon," Rami Abdel Rahman, head of the Britain-based monitor.
An SDF spokesman, Kino Gabriel, said the Kurdish-Arab alliance had repelled several ISIS counter-attacks and was now advancing from three different directions.
The SDF reported in a statement on Sunday that it had moved 1,000 civilians away from the fighting.
More than 5,000 civilians have fled their homes since December 14, when the SDF took Hajin, which had been the largest ISIS-held town along the Euphrates River valley, according to the monitor.
The recapture of Al Shaafa and Sousa will cap a four-year multinational effort to smash the sprawling "state" ISIS declared over parts of Syria and Iraq in 2014.