'We're all worried about more confrontation' between Iran and others, says the U.S. special envoy for Yemen

Tim Lenderking, U.S. special envoy for Yemen, tells CNBC's Hadley Gamble that there are concerns about more confrontation between Iran, the Gulf countries and the U.S. It comes against the backdrop of continued talks between the U.S and Iran to revive a 2015 nuclear deal.