the united nations security council met in an urgent sessions calling on all sides to put down their weapons and negotiate. a u.s. official warning that yemen is in a rapid downward spiral and at the edge of civil war. let's bring in the latest with correspondent nic robertson. >> reporter: christine, this is a dangerous escalation in yemen. yemen is where al qaeda in the arabian peninsula is based where uss cole was attacked. it was where the under pants bomber was located. al qaeda is taking advantage of the unstable situation. the people appear to be the houthi rebels entering by air and land in the city of taiz.