"It [US troop deployment] is part of an incremental buildup to be seen as preserving the transportation lines and oil flow in the region", Kwiatkowski said. "The Pentagon has long understood that no sustained ground or air war against Iran is winnable or desirable".

Earlier in the day, Tehran and Washington took a step closer towards full blown confrontation after a US drone was shot down by the Iranians who claimed it violated the country's airspace. The incident comes on the heels of the Pentagon deploying more than 1,000 troops to the region over recent attacks on oil tankers in the Gulf of Oman.

Although US President Donald Trump initially said Iran made "a very big mistake" he later told reporters he doubted the drone shoot down was intentional. On Wednesday, US envoy Brian Hook told Congress the latest Mideast troop deployment was a defensive move and no offensive operations are being considered.