US Secretary of State John Kerry told Gulf Arab states on Thursday Washington was not seeking a "grand bargain" with Iran, and said a nuclear deal with Tehran would be in their interests.
The United State's Gulf allies, particularly the Sunni Muslim kingdom of Saudi Arabia, are concerned that Shi'ite Iran will gain from any agreement to end years of dispute over its nuclear ambitions.
"Even as we engage in these discussions with Iran around its nuclear program, we will not take our eye off of Iran's other destabilising actions in places like Syria, Lebanon, Iraq and the Arabian peninsula, Yemen particularly," Kerry said after meeting Saudi King Salman and Foreign Minister Prince Saud al-Faisal.
"Let me underscore: we are not seeking a grand bargain. Nothing will be different the day after this agreement, if we were to reach one, with respect to all of the other issues that challenge us in this region."
Kerry also met the foreign ministers of Kuwait, Qatar, Bahrain, the United Arab Emirates and Oman.
The US secretary of state arrived in Riyadh late on Wednesday from Montreux, Switzerland, where he said he had made progress in talks with Iranian Foreign Minister Mohammad Javad Zarif.
Gulf countries, like Israel and many Western states, fear Iran is using its atomic program to develop a nuclear weapons capability, something Tehran denies.
Saudi Arabia regards Iran as its main regional rival and the two countries back opposing sides in wars and political struggles across the region, often along sectarian lines.
Saudi Arabia and its allies worry that a nuclear accord will not stop Iran from gaining the bomb. They are also concerned it would ease international pressure on Tehran and give it more room to intervene in regional issues.
Speaking alongside Kerry, Prince Saud said Saudi Arabia was concerned by the involvement of Iran in the push being made by Iraqi forces alongside Shi'ite militias to retake the city of Tikrit from Islamic State.
"The situation in Tikrit is a prime example of what we are worried about. Iran is taking over the country," he said.
Prime Minister Benjamin Netanyahu said in a speech to the US Congress on Tuesday a deal with Iran would be "a countdown to a potential nuclear nightmare".