washington u.s. president donald trump thursday urge members u.n. security council back renewal international inquiry chemical weapons attack syria say need prevent president bashar al-assad use arm need un security council vote renew joint investigative mechanism syria ensure assad regime commit mass murder chemical weapons ever trump say note twitter 15-nation council due vote thursday rival u.s. russian bid renew international inquiry diplomats say wednesday move could trigger russia 10th veto block action syria trump urge u.n. council renew syria chemical arm inquiry