U.S. Defense Secretary Ash Carter says Saudi Arabia's King Salman and his defense minister have supported the Iran nuclear deal but have expressed doubts about how effectively the historic agreement with six world powers would be enforced.

Speaking after meeting with the Saudi king and Defense Minister Muhammad bin Salman al-Saud in Jeddah on July 22, Carter said the Saudis "reiterated their support" for the deal.

He said: "The only reservations we discussed were ones that we clearly share, namely that we attend to verification of the agreement as it's implemented," and the use of a "snap-back" mechanism to quickly reimpose sanctions if Iran cheats on any part of the agreement to refrain from developing nuclear weapons.

Carter's visit is part of a regional tour aimed at reassuring Washington's allies about the deal with Iran.

By Radio Free Europe/Radio Liberty