Terming the killing of Osama bin Laden the most significant achievement against the al-Qaeda, a top White House official on Sunday said the U.S. was now looking for his deputy, Ayman al Zawahiri, who is likely to be the new chief of the terror outfit.

“Al Zawahiri will be the next number one terrorist that we're looking for in the world. But we have a broad and global effort,” National Security Advisor Tom Donilon told CNN in an interview.

Seeks access

The U.S. has demanded access from Pakistan to all non-combatants, including Osama bin Laden's three wives, detained by the Pakistani authorities, and additional materials recovered from the Abbottabad compound where Osama was living for the last six years. Talking to ABC News, Mr. Donilon said: “We need to work with them [Pakistan] on assessing all the evidence….”