Pakistan has not taken necessary action against Hafiz Saeed, Secretary of State Hillary Clinton said on Monday, referring to the Islamist suspected of masterminding an attack by Pakistan-based gunmen on the Indian city of Mumbai in 2008.
India has repeatedly called on Pakistan to bring Saeed to justice, an issue that has stood in the way of rebuilding relations between the nuclear-armed neighbours since the carnage in India's financial capital, where gunmen killed 166 people.
India is furious Pakistan has not detained Saeed, despite handing over evidence against him.
Washington has offered a reward of $10 million for information leading to Saeed's capture.
"We're well aware that there has not yet been the steps taken by the Pakistani government to do what both India and the United States have repeatedly requested them they do," Clinton said in the Indian city of Kolkata.
"And we're going to keep pushing that point. 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 also said that the United States believes al-Qaeda leader Ayman al-Zawahiri is somewhere in Pakistan.
(Reporting by Andrew Quinn; Writing by Matthias Williams; Editing by John Chalmers)