U.S. Secretary of State John Kerry said Thursday during a visit to Riyadh, Saudi Arabia, that Washington was keeping an eye on Iran’s “destabilizing” actions in the Middle East, a gesture meant to reassure the Gulf kingdom that ongoing nuclear talks with the Islamic Republic would bring stability to the region. Iran’s involvement in the ongoing offensive against ISIS fighters in Iraq was a “prime example” of what worried Saudi Arabia, said Saudi Foreign Minister Saud al-Faisal according to Reuters.

"Even as we engage in these discussions with Iran around its nuclear program, we will not take our eye off of Iran’s other destabilizing actions in places like Syria, Lebanon, Iraq and the Arabian peninsula, Yemen particularly," Kerry said during a joint press conference with al-Faisal. Kerry’s attempt to assuage Saudi concerns about the nuclear deal came after the secretary of state made progress in talks with Iranian Foreign Minister Mohammad Javad Zarif in Switzerland.

Saudi Arabia, along with its Sunni Arab allies, has worried that regional rival Iran would grow more powerful if a nuclear deal was signed, bringing an end to some of the international sanctions that have crippled the Shiite nation’s economy. Tehran’s recent efforts to boost its regional position, particularly through its involvement in Iraq, already have the Saudi government on edge. “Iran is taking over Iraq,” al-Faisal said to reporters at the conference, according to Al-Arabiya.

Iranian-backed Shiite militias are playing an active role in the recently launched Iraqi offensive against Tikrit, which has served as a stronghold of the Islamic State group since militants captured the city in June. Iranian military commander Ghasem Soleimani, who leads the powerful Revolutionary Guard’s Quds Force, is said to be coordinating operations on the eastern flank of the offensive, in a sign of Tehran’s robust involvement in the fight. The U.S.-led coalition fighting ISIS in Iraq and Syria has not participated in the Tikrit offensive.