The United States is monitoring information indicating that North Korea may be running a large underground military base in Syria that could be used for advanced weaponry and nuclear-related work, according to regional reports and U.S. officials tracking the situation.

Regional reports have begun to surface indicating North Korea has neared completion of the construction of an underground military base located near the hometown of embattled Syrian President Bashar al-Assad.

According to satellite images and a military source the underground facility has been under construction for seven years and the high level of secrecy and tight guard at the North Korean base raise speculations whether it’s a nuclear facility or overseas depot for North Korean weapons.

U.S. officials have said they are monitoring these reports and efforts by North Korea to help Assad rebuild Syria’s chemical weapons factories. The Trump administration has been engaged in efforts to counter North Korea’s proliferation in Syria, particularly its efforts to supply Assad with chemical weapons.

But the underground North Korean military base could be hiding more than just chemical weapons, according to regional reports indicating that the sheer size of the base, which is mostly situated within a mountain, raises concerns of nuclear work.

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