Last week’s announcement of another 200 US troops being deployed to Jordan with an eye on Syria could rapidly become 20,000, officials say, if the decision is made by President Obama to move beyond external aid to rebels to overt military intervention.

Even the 20,000 deployment is one of the more modest schemes among the many different plans considered by the Pentagon for a Syrian invasion, and in December they conceded one of the plans involved a minimum of 75,000 troops.

When unveiling the 200 troop plan, Secretary of Defense Chuck Hagel did not immediately lay out the 20,000 option for the Senate, but rather has focused on warning the Senate against such a war, saying that it would rapidly escalate far beyond anything they presently envision.

Indeed, Hagel’s testimony reflected a growing rift between the Pentagon’s leadership and the State Department, which under John Kerry has grown increasingly eager to intervene in Syria. Hagel’s testimony has focused on avoiding heedlessly starting a “lengthy and uncertain” war.