Of course there wasn't Western intelligence proving it. If it had been proven, they'd exist. The intelligence simply pointed to the high probability; that coupled with other variables (such as bad information), made it probable enough for WMD to exist, and western intelligence then decided to posit that they did exist.
Just to make it clear, I'm not vouching that a just war occurred here. I'm just saying that similar intelligence existed for many western nations and each nations interpretation differed.
As much opposition existed, the intelligence other nations had and their interpretation led them not to refute U.S. moves, but instead offer assistance .These allies include Albania, Azerbaijan, Bulgaria, the Czech Republic, Denmark, the Dominican Republic, El Salvador, Estonia, Georgia, Holland, Honduras, Hungary, Italy (which has contributed some 3,000 troops), Kazakhstan, Latvia, Lithuania, Macedonia, Mongolia, Nicaragua, Norway, Poland, Portugal, Romania, Slovakia, South Korea, Spain and Ukraine.
Why would the secret service send a letter out? That has nothing to do w/ the role of the secret service. Now I could understand a letter being sent out, but it would surprise me that the USSS would get their nose wet in internal politics.
Anyway, I'm not really taking any side here, I'm trying to expose how grey areas do exist. I can't honestly say things are clear cut in any way.