Secretary of State Hillary Clinton said Monday the United States believed the chief of Al-Qaeda was in Pakistan and she vowed to keep up pressure on Islamabad to find other "most-wanted" militants.
"We want to disable Al-Qaeda and we have made a lot of progress in doing that," Clinton told an audience in India, a week after the one-year anniversary of the killing of Osama bin Laden in Pakistan by US special forces.
"There are several significant leaders still on the run. Zawahiri, who inherited the leadership from Bin Laden is somewhere, we believe, in Pakistan," she added.
Ayman al-Zawahiri, an Egyptian cleric, was second-in-command under bin Laden and was regarded by US intelligence agencies as chief ideologue for the militant group.
Clinton also said the US would continue to press for the arrest of the founder of Pakistan-based militant group Lashkar-e-Taiba (LeT) who is wanted over the 2008 Mumbai attacks.
The United States last month offered a $10 million reward for information leading to the conviction of Hafiz Saeed, who lives openly in Pakistan and is considered a mastermind of the assault in India that killed 166 people.
Clinton on Monday said she was "well aware" that the Pakistani government had not yet taken steps to help secure Saeed's conviction.
"We're going to be pushing that. So it's a way of raising the visibility and pointing out to those who are associated with him that there is a cost for that," Clinton said of the reward offer.
Three of the top five most-wanted militants by the United States are believed to be in Pakistan, including the leader of the Afghan Taliban, Mullah Omar.
But Clinton, addressing a public forum in Kolkata, said she also appreciated sacrifices by Pakistan, saying that it was the main victim of violence by extremists.
Saeed has openly defied the US announcement by holding press conferences in Pakistan. The United States has said it is not offering the reward for his capture but for information to prosecute him.
He was put under house arrest in Pakistan a month after the Mumbai attacks, but was released in 2009 and in 2010 the Supreme Court upheld his release on the grounds that there was insufficient evidence to detain him.
India welcomed the bounty, saying it reflected the commitment of India and the United States to bring the perpetrators of the Mumbai attacks to justice.