Kerry and Saudi Foreign Minister Adel al-Jubeir presented a united front when they spoke at a news conference after a meeting of foreign ministers from the Gulf Cooperation Council.
The Gulf states have sided with the kingdom in its spat with Iran and backed the rebels fighting to overthrow Syrian President Bashar Assad, a key ally of the Islamic Republic.
Kerry and al-Jubeir said the US and the GCC agreed on the need to confront destabilizing Iranian activities in the region and on an unspecified "understanding" that will allow the UN-led Syria negotiations to begin next week as planned.
Al-Jubeir denounced Iran for its "hostile and aggressive stance" against Arab nations. But he said he did not believe that the Washington would act rashly in dealing with Tehran because of the nuclear deal just put in place. It has given Tehran access to billions in formerly frozen assets.
He took a swipe at Iran by noting that in the prisoner swap that resulted in the release of four imprisoned Americans in Iran, none of the seven Iranians cleared of charges in the United States opted to return to Iran. It "tells you what a great country Iran is that no one wanted to return to it." Six of the seven are dual nationals.