US Secretary of State Mike Pompeo, one of the architects of Washington's hard-line policy on Iran, has relayed a message to Tehran that the death of a single US service member would trigger a military response, the Washington Post reports.
According to the broadsheet, one such message was sent during Pompeo's emergency visit to Baghdad, after the White House picked up intelligence allegedly showing that Iran or its proxies were threatening US interests in the Middle East.
A person with knowledge of the situation was quoted as saying that Pentagon officials, including outgoing Acting Defence Secretary Patrick Shanahan, have been "the ones putting the brakes" on hawks at the State Department and the White House.
However, Shanahan's upcoming departure from Pentagon's top slot is understood to have raised concerns that the more belligerent Trump administration will push the military aside and involve it in further escalation of the conflict.
Gen. Paul Selva, the nation's second-highest-ranking military officer, warned on Tuesday that "if the Iranians come after US citizens, US assets or the US military, we reserve the right to respond with military action," and that would also apply to Iranian-aligned militias in the Middle East.
"The evidence points towards Iran," Selva told reporters. "The only perpetrator in the area that has a motive to perpetrate it is Iran," he said.
"Our history in the region is we have threatened to respond and not responded. It would be a miscalculation on the part of the Iranians to believe that that's going to persist."
On Monday, the Pentagon gave a go-ahead to the dispatching of an additional 1,000 troops to the Middle East, following last month's military build-up.
Comment: If that is the line, it leaves many opportunities for Iran and their allies to make life miserable for the Americans and their allies without triggering a military response. (Barring a false flag that blames the Iranians for the death of one or more American service members, of course.) Whether or not they have begun to do so yet is unverifiable, but the possibility is there.