Even in the UK the truth is a valid defense against a libel case. The main difference is that the burden of proof is put on the alleged libeller, who has to prove s/he hasn't committed libel, rather than on the person who has supposedly been libelled.
IIRC the US requires that you prove the libeller knew it was false as well.
Basically if you act on good faith you are clear, even it isn't true. (Note that there are requirements that you took some measures to verify the legitimacy depending on your position).
