Claes denied categorically that they had ever known of the existence of an Agusta proposal, and told the NATO ambassadors that he did not know anything about an Agusta payment to the Socialist Party.
Claes told the NATO ambassadors what he knew.
It is correct, because Claes said he denied knowing about the Agusta payment, and that is what he knew. 
( z1 tell :ARG0 ( z2 person :name ( z3 name :op "Claes" ) ) :ARG1 ( z4 thing :ARG1-of ( z5 know :ARG0 z2 ) ) :ARG2 ( z6 ambassador :mod ( z7 military :name ( z8 name :op "NATO" ) ) ) )