sentence analysis help

[mandarias]

I'm practicing for my grammar exam and found this old exam question, can someone tell me how they would analyze this so i can compare with my own suggestion.

The Bush administration admits it was mistaken in believing that Saddam Hussein had weapons of mass destruction.

Thanks

[mandarias]

My primary questions is if the; that-clause is an Adverbial or a Direct Object or something completely else

[Buddhaheart]

‘That Saddam Hussein had weapons of mass destruction.’ is a noun clause as it answers the question ‘in believing what?’

[fiona bramble]

‘That Saddam Hussein had weapons of mass destruction.’ is a noun clause as it answers the question ‘in believing what?’

Yes, that's it! It is the direct object of the verb "believing". If I broke it down further, I believe that the "in believing" has been reduced from "when it believed", so that may be the "adverbial" you are thinking of. I'm not sure if "in -ing" is an established adverb reduction though...interesting!

Fiona