Washingon (CNN) A US intelligence assessment conducted in recent days has concluded that Iranian-backed militias and proxy forces could be planning a strike against US military forces or interests in the Middle East, according to three defense officials.

Officials emphasize their concern centers around the threat from those militias located in Syria and several other locations in the Middle East. They all describe the potential threat as ongoing and worrisome. However, they would not describe the specific intelligence that continues to be gathered.

These militias have increased access to ballistic missile and other advanced weapons inventories as Iran continues to move weaponry into Syria.

While there are no specific indicators of an Iranian attack, the concerns stem in part from Iran's statements that the US was one of the countries behind an attack on an Iranian military parade this month that killed at least 29 people.

National security adviser John Bolton's issued a stark warning to Iran at the United Nations General Assembly on Tuesday, "If you cross us, our allies, or our partners; if you harm our citizens; if you continue to lie, cheat, and deceive, yes, there will indeed be hell to pay."

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