There is no indication that the attackers of a US base in Syria's northeastern province of Al-Hasakah were aware that air defense systems were not fully operational, US National Security Council Special Communications Coordinator John Kirby claimed on Sunday.

On Friday, The New York Times reported that the United States was investigating the reason why its air defense system was not fully operational during a strike on the US base in Syria.

The US military currently has no knowledge as to why the system did not work as it should, and the circumstances are being investigated at present time, the report said, citing two officials.

"We've seen no indication that they had ... that kind of knowledge," Kirby told the CBS News broadcaster.

"They have used similar capabilities to go after our troops and our facilities there in Syria. So there's no indication that they would have had knowledge of that," he added.

On Friday, several rockets and drones targeted US occupation bases in the Conoco gas field and Al-Omar oil field east of Deir Ezzor, Eastern Syria.

A few hours before, the US military said it carried out "precision airstrikes" in eastern Syria in response to an alleged drone attack that killed one American and injured five US service personnel.

A Department of Defense statement claimed that the casualties fell "after a one-way unmanned aerial vehicle struck a maintenance facility on a Coalition base near Hasakah in northeast Syria."

The statement further added that the US intelligence community assesses "the UAV to be of Iranian origin."

US Defense Secretary Lloyd Austin said that at the direction of President Joe Biden, he had authorized precision airstrikes in eastern Syria "against facilities used by groups affiliated with Iran's Islamic Revolutionary Guards Corps."

Al Mayadeen correspondent in Syria reported that the US aggression targeted the Rural Development Center and the Grain Center near Deir Ezzor Military Airport.

On Saturday, Syria slammed the savage aggression carried out by the US occupation forces on several areas in the Deir Ezzor Governorate that resulted in the killing of a number of people, the wounding of others, and material damage.

It is noteworthy that the US has for long employed the alleged "ISIS threat" as a pretext to continue its illegal occupation of northeastern Syrian territories.

US occupation forces frequently loot oil from Syrian gas fields and transport them to other occupation bases in Iraq via illegal crossings.

In early March, the US House of Representatives voted against legislation instructing Biden to end the US occupation of the Syrian Al-Tanf region and remove approximately 900 troops.

Currently, the US army and other foreign forces, participating in the so-called "International Coalition", occupy no less than 28 declared military sites in Syria, distributed over three governorates: Al-Hasakah (17 sites), Deir Ezzor (nine sites), and Homs (two sites).

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