Heir Sheikh Meshaal al-Ahmad al-Jaber al-Sabah, 83, replaces Sheikh Nawaf who had ruled for three years.
Leaders of six Gulf countries and Turkey meet in Qatar, with Israel’s war on Gaza at the top of the agenda.
Communique coinciding with Antony Blinken’s visit to Saudi Arabia backs two-state solution based on 1967 borders.
Experts say many Arab governments see last month’s earthquake disaster as reason to deepen engagement with al-Assad.