The United States suggested Thursday it was open to a “new arrangement” with Iran for peacefully resolving disputes such as Tehran’s recent ballistic missile tests, while America’s Sunni allies in the Persian Gulf said Iran must stop sending forces to Syria and weapons to Yemen if it wants to normalize ties with its neighbors. Setting the stage for President Barack Obama’s summit with regional leaders in Saudi Arabia later this month, U.S. Secretary of State John Kerry met with the foreign ministers of the six-nation Gulf Cooperation Council to advance a series of proposals aimed at easing Arabs’ concerns about...