U.S. Secretary of State Marco Rubio is visiting Gulf countries, including the United Arab Emirates, to reassure allies about a new U.S.-Iran agreement aimed at ending regional hostilities.

The deal, negotiated after recent diplomatic talks, proposes reopening the Strait of Hormuz, easing sanctions, and continuing negotiations over Iran’s nuclear program.

Gulf states remain concerned that the agreement does not fully address Iran’s missile program and support for regional proxy groups.

Rubio argued that the deal requires a broader end to Iranian-backed violence and insisted the Strait of Hormuz must remain an open international waterway free of tolls or fees, the AP has reported.

He is meeting regional leaders in the UAE, Kuwait, and Bahrain to explain and defend the agreement’s terms.