WASHINGTON - US Republican presidential candidate Donald Trump insisted on Sunday he was "100 percent right" when he said he saw Muslims in Jersey City, New Jersey, cheering the 9/11 attacks on the World Trade Center even though fact-checkers have debunked his claim.In a phone interview on NBC's Meet the Press, Trump said he was getting an "unbelievable response" from "hundreds" of people who told him they also saw televised Muslim celebrations of the Sept. 11, 2001, attacks in Manhattan."I saw it. So many people saw it. And, so, why would I take it back? I'm not going to take it back," said Trump, who has been among the most vocal of the Republican candidates in the race for the November 2016 election in expressing skepticism about Muslims living in the United States.