WASHINGTON, May 12: Saudi King Salman phoned US President Barack Obama on Monday to “express his regret” for missing a high-profile summit at the White House and Camp David this week, and review the agenda for the meeting with Gulf leaders, the White House said. The leaders agreed they need to work with other Gulf states “to build a collective capacity to address more effectively the range of threats facing the region and to resolve regional conflicts,” the White House said, noting the leaders agreed on the need for urgent humanitarian aid in Yemen. (AGENCIES)