NEW YORK -- The US Department of the Treasury on Tuesday put 27 Iranian airlines on its Specially Designated Nationals List thus targeting all remaining Iranian airlines in a bid to step up pressure on Iran.

Targets include nine companies based outside of Islamic Republic, but unclear if Chinese firms to face sanctions, as US seeks to up economic pain on Tehran after 6 months of war

The US Treasury Department said the action was aimed at grounding Iran's Mahan Air, already sanctioned by the US and the European Union, and all other Iranian airlines.

The US Treasury announced new sanctions on 36 entities, including 27 Iranian airlines, for “supporting Iran’s aviation sector”.