According to a senior U.S. official, American intelligence networks have intercepted “chatter” from an al Qaeda member in Pakistan that shows intent to launch a terrorist attack in New York or Washington this weekend. Officials say the source has given accurate information before. The attack reportedly is pegged to the anniversary of 9/11 and suggests that Ayman al-Zawahiri, al Qaeda’s new head, is behind the plot. Earlier, Hillary Clinton confirmed that al Qaeda was behind the threat on New York City. Security officials are searching for three men believed to have entered the country in August, including one U.S. citizen. Early reports said they were looking for two rental trucks, but they have since been recovered and proved to have no connection to the suspected plot. Meanwhile, New York City is ramping up security in subways, bridges, tunnels, and other potential targets.