Funny, because the NATO and the US have been unwilling to do anything in Syria despite public criticism for how long now? They don't need a legit reason to invade to keep the people calm, they need a legit reason to stay out of Syria to keep them calm. If something like what your proposed was the case, I don't think they'd hold out for such a long time, I mean no one is gonna trust these stories anyway, so why should they care so much about making it seem like there's no immediate connection? The unrest created by the alleged favouritism of the NATO is much more noteworthy than what interening in both states would cause. Get fucking real.
Syria's situation became more definitive especially with the involvement of chemical weapons
The biggest threat to international relations is the use of WMDs
If Syria's government is free to use chemical weapons on the rebels, it will mark a future where no one country can be held accountable for using any WMD. Both the rebels and the Syrian government have no signs of stopping. The only thing the world should do is watch the airspace.