President Donald Trump stressed the need for Gulf unity in talks with Saudi Arabia's King Salman, amid a crisis that has divided several key US allies in the region.
The two men spoke by phone at Riyadh's initiation after Saudi Arabia broke relations and imposed a blockade on its smaller neighbour Qatar over funding for Islamist groups and a host of other conflicts.
"The two leaders discussed the critical goals of preventing the financing of terrorist organisations and eliminating the promotion of extremism by any nation in the region," the White House said in a statement.
"The president underscored that a united Gulf Cooperation Council is critical to defeating terrorism and promoting regional stability."
Trump earlier appeared to weigh in firmly behind efforts to isolate Qatar, which is home to the largest American airbase in the Middle East.