The United States is taking seriously the intelligence tip of a possible al-Qaeda plot to hit Washington or New York. White House top counter-terrorism official John Brennan said in an interview that the US knows it is specifically related to both Washington and New York and it is credible in terms of the source that it comes from. He said that President Barack Obama has been taking meetings with his top national security and intelligence teams on this issue. President Obama and his predecessor and political rival George W Bush along with their wives led the world in mourning the loss of nearly 3,000 lives, exactly 10 years ago in the most fearful terror attack in the United States. Dressed in black, the two couples held hands as they walked slowly along the memorial in New York, watching the wall etched with names of the 2,983 people killed in the terror unleashed by al-Qaeda chief Osama bin Laden. Obama did not make any speech, but read a passage from the Bible.