How does Iago lie at the beginning of Act 1 Scene 2

Iago continues his deliberate misrepresentation, swearing to Othello that he could have killed Roderigo for his actions (He tells Othello that Brabantio is upset, and will probably try to tear Desdemona from him). Really Iago is using Roderigo to in his evil plan to undo Othello. 

He's saying that he would kill roderigo if he wanted to but he's actually teamed up with roderigo