In the sentence, "Diplomats said a Russian chemical weapons attack in Ukraine, or a heavy bombardment of the capital Kyiv, could be a trigger for an energy embargo," I am confused whether the modal verb COULD here is used in the temporal or hypothetical sense.
On one hand, I think it's hypothetical because the proposition is speculative and has not yet happened. On the other, the main verb here is "said," which indicates that COULD here is a backshifted form of CAN.
Collins (Modals and Quasi-modals in English, 2009) gives the example, "He said the Federal Government's approach could lead to reduced investment" and classifies COULD as temporal, but I genuinely feel that this is incorrect because it's speculative, so how could it be temporal when it didn't happen? He also writes that this sentence expresses epistemic meaning, which I don't agree with because that would mean that its forward-shifted (idk if that's a word) form would be CAN, and CAN only expresses epistemic meaning in the negative form. This leads me to believe that he may have made a mistake in analyzing this utterance, but I can't entirely be sure.
Could someone share their thoughts on this?