washington u.s. secretary state rex tillerson authorize state department notify congress trump administration sale precision-guided munition saudi arabia use yemen campaign senior u.s. diplomat say tuesday notification one last step arm sale process trigger formal 30-day review allow members congress attempt pass legislation stop sale u.s. lawmakers introduce legislation last week seek block 500 million 110 billion arm sale saudi arabia include portion precision-guided missiles offensive weapons announcement sale expect march objections mostly democratic lawmakers human right group lead washington ask riyadh commitments improve target procedures would minimize civilian casualties ask tuesday whether saudis take specific measure improve target capabilities senior u.s. diplomat act assistant secretary state near eastern affairs stuart jones answer directly continue source conversation us jones tell reporters constantly try improve process yemen civil war pit iran-allied houthi rebel government back saudi-led arab coalition nearly 4,800 civilians kill since march 2015 unite nations say march jones say tillerson authorization expect occur president donald trump may 20-21 visit saudi arabia trump predecessor barack obama december limit military support saudi arabia campaign yemen concern civilian casualties halt sale precision-guided munition trip saudi arabia trump receive warm welcome gulf arab leaders want crack iran influence region commitment find lack obama trump also make overt mention human right abuse saudi arabia speech move criticize democrats republicans congress fact feature speech mean part bilateral dialogue jones say take public debate conversations directly quietly effective tillerson last week tell reporters human right issue central part trump private meet saudi officials instead focus fight terrorism path clear congress consider u.s. arm sale riyadh state department