(1) What the UN says matters since
(a) the legitimacy of the American-Briitish operations vis-a-vis the rest of the world rests on the facade of international approval via the UN. It may come as a surprise to many, but breaking the facade of respect for international law does not win one respect, and leads to decline in support for US actions generally. Given the role we play (I mean US’s self-defined position) keeping up a rep is in fact important.
(b) the US and Britain also desire to keep together the last vestiges of support for the sanctions regime, which in turn requires UN support for legality. Unilateral blockades and sanctions are not only fruitless, such actions tend to rebound.
(2) Saddam as a threat.
(a) I am unaware that the Iraqis are developing more advanced air defense. They may be buying more advanced systems on the black market, probably from E. Euro, Chinese or Russian sources, but this is hardly ‘developing’.
(b) as I have argued elsewhere Saddam’s threat must be rationally compared to the results of policy towards Iraq, which may result in worse problems in the long run. I am thinking of long-term tensions in the Arab world. Even among pro-American Arab opinion, I find zero support for current US policy. That in and of itself does not mean abandoning it. However, it does suggest that fear-mongering emotional policies toward Iraq need to be rationally re-examined in terms of the costs and benefits.