Is Trump leading the US on a warpath with Iran?

Washington and Tehran dial up war of words as risk of another military action in the Middle East rises.

On a spring morning in 2016, a retired four-star general, who was forced out of his job by then-President Barack Obama, spoke before defence and foreign policy experts gathered just blocks from the White House.

The 65-year old speaker, with silver hair and puffy eyes, was blunt. For all the dangers al-Qaeda and the Islamic State of Iraq and the Levant (ISIL, known as ISIS) pose in the Middle East, he warned that the Iranian regime "is the single most enduring threat to stability and peace".

He recalled that as commander of US troops in the Middle East, the first three questions he would ask his subordinates every morning "had to do with Iran and Iran and Iran".

"We only pray, the rest of us outside this town, that someone good is listening here," he told the Washington crowd, as he issued an ominous prediction: "The future is going to be ghastly", and that "the next president is going to inherit a mess".

Nine months later, James Norman Mattis returned to the US capital as defence secretary of President Donald Trump.

As the man who oversees the 1.3 million US troops, manages Pentagon's $582.7bn budget, and directs military policy, Mattis has Trump's ear. The US president fondly calls him "Mad Dog Mattis", although the former general refers to himself as "Chaos", his Marine call sign.

Supporters said he is best suited for the defence job because of his combat experience in Iraq and Afghanistan, as well as his "strategic mind". Former US defence chief Robert Gates called him a "warrior-scholar".

But critics said Mattis' fixation with Iran, combined with the president's hostility towards the oil-rich Gulf state, could lead the United States into a replay of Iraq - only this time with a much more "disastrous" consequence to the region.

Media reports had suggested it's the same eagerness for confrontation with Iran that prompted Obama to fire Mattis as Central Command chief in 2013, at a time when the US and other world powers were trying to engage Tehran and secure a nuclear deal.