Actually, they did not want US to attack Iraq:

https://forward.com/opinion/9839/sharon-warned-bush/

He didn't say not to attack. It says in there that he told Bush that Iraq was a threat, but that he shouldn't occupy Iraq or try to build a democracy there because it won't work. The rest of the article is 2007 hindsight.

He would have never been there if not for the USA in the first place...