The United States today asked Pakistan to take appropriate steps to prosecute those responsible for the Mumbai terrorist attack that killed 166 people and injured over 300 in November 2008. State Department spokesman P J Crowley told reporters in Washington that the US have repeatedly called upon Pakistan to prosecute those responsible for the attack, and continue to expect Pakistan to take appropriate steps in this regard. He said, the matter is being raised by the US with Pakistan on a regular basis.Crowley was responding to questions by the media about a report published in The Washington Post which said that at least half a dozen key masterminds of the 26/11 are at large in Pakistan and there is increasingly strong evidence of ISI's link to this major terror attack assault.