WASHINGTON - The United States Sunday dismissed a claim that President Asif Ali Zardari and his ambassador to US Husain Haqqani had prior knowledge of the May 2 American military operation in which Osama bin Laden was killed. "Reports claiming Ambassador Haqqani or President Zardari had advance knowledge of the May 2 Abbottabad operation are groundless, a White House spokesperson, Caitlin Hayden, said.