LONDON - Had President Donald Trump ordered it, the United States military could have struck hard at targets in Syria almost instantly after news emerged of a suspected use of chemical weapons by the Syrian regime of President Bashar al-Assad.

But preparations for the punitive military operation have taken almost a week partly because Washington was keen to forge a broader coalition for such action, but also because military planners are eager to calibrate the dual objectives of both executing a strike which is forceful enough to deter Syrian President Assad from ever again using chemical weapons but at the same time does not trigger off a broader US-Russia military confrontation.