BAGHDAD, May 15 (Xinhua) -- The U.S. military said on Wednesday that the U.S. forces are on high alert in Iraq and Syria over fears of "imminent threats" from Iran-backed forces in the region.

"U.S. Central Command, in coordination with Operation Inherent Resolve (OIR), has increased the force posture level for all service members assigned to OIR in Iraq and Syria," U.S. Central Command spokesman Bill Urban said in a statement.

OIR, responsible for the U.S. military intervention against the Islamic State militant group, "is now at a high level of alert as we continue to closely monitor credible and possibly imminent threats to U.S. forces in Iraq," Urban added.

The high alert was based on "credible threats available to intelligence from U.S. and allies regarding Iranian-backed forces in the region," the U.S. spokesman noted.

The U.S. military move came amid the tense situation in the region after U.S. President Donald Trump decided not to re-issue the sanctions waivers for major importers to continue buying Iran's oil when they expired in early May.

The United States has also increased its military buildup in the region recently by deploying an aircraft carrier, bombers and anti-missile systems there, citing a threat of Iranian attack.