(CNN) The US government has assessed that Israel was likely involved in a strike that took place north of Baghdad last month, a strike that has complicated America's relationship with Baghdad, according to two US officials.

The strike, believed to be Israel's first in Iraq in several decades, likely targeted militia groups that have a close relationship with Iran.

The officials added that the US is looking at several possible scenarios that could involve Iran or its proxies carrying out an attack in retaliation.

The US has some 5,200 troops in Iraq, where they assist Iraqi forces battling the remnants of ISIS.

The US has refused to officially say whether Israel was involved but has denied any responsibility for the strike, saying Iraq's sovereignty should be respected.

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