But that has been rejected by Democratic politicians on the panel that had summoned Rove, saying his claim of immunity is invalid.

Following his refusal to appear on Thursday they ruled that the former advisor was breaking the law by refusing to cooperate - a possible first step toward holding him in contempt of congress.

Rove was subpoenaed in May in an effort to force him to talk about whether he played a role in prosecutors' decisions to pursue cases against Democrats or in firing federal prosecutors considered disloyal to the Bush administration.

A decision on whether to pursue contempt charges now goes to the full Judiciary Committee and ultimately to Nancy Pelosi, the speaker of the US house of representatives.