During his visit to Saudi Arabia to attend the Gulf Cooperation Council (GCC) summit, President Obama provided the GCC member nations with a personal guarantee that the United States would defend their nations against “Iranian aggression.”
The comments were intended to placate the GCC member nations, particularly Saudi Arabia, as they are all openly angry about the US involvement in the P5+1 nuclear deal. Obama insisted that despite the deal, the US has “serious concerns about Iran’s behavior.”
The offer is likely an empty one, since Obama’s comments do not constitute a treaty of defense, and with him out of office in just eight months, it would be up to future presidents to decide if they actually wanted to get involved in future wars in the region.
Ultimately, of course, an empty pledge is as good as a real one, since Iran has never expressed serious interest in attacking any of the GCC nations, and spends far less on its military than either Saudi Arabia or the UAE, meaning there is no practical way they’d ever launch such a war.