The choice to hold such data back rests in the hope that, while it remains an open secret, there might be opportunities to dial down the dangers of war in the Gulf through diplomacy.
The extent of the urgency of achieving this was visible at the United Nations General Assembly last week where the French led efforts to lead the US and Iran towards talks.
Acknowledging a brazen act of violence against a sovereign nation would almost inevitably demand a violent response from that nation or her allies and put an end to diplomacy.
The gamble for Trump and other leaders is that a reluctance to act, in retaliation for what was a strategically effective attack on Saudi Arabia, may be seen in Tehran as weakness.
And that could result in a further escalation which, in the view of many sources in diplomacy and intelligence across the region, would most certainly trigger a conflict.
Attacking Iran would set off a complex war that simply could not be won by the West and its allies — and could easily be lost.
So far operations that the US has blamed on Iran against shipping in the Persian Gulf, Saudi Arabia’s oil industry and the downing of a US drone have been bloodless.
However much the Iranians deny their involvement, it seems their actions hae been carefully calibrated to signal greater dangers to come — and Iran’s military reach.