WASHINGTON (AP) — Vigorously defending American attacks in Libya, President Barack Obama declared Monday night the United States intervened to prevent a slaughter of civilians that would have stained the world's conscience and "been a betrayal of who we are" as Americans. Yet he ruled out targeting Moammar Gadhafi, warning that trying to oust him militarily would be a mistake as costly as the war in Iraq.Obama announced NATO would take command over the entire Libya operation Wednesday, keeping his pledge to get the U.S. out of the lead fast — but offering no estimate on when the conflict might end and no details about its costs despite demands for those answers from lawmakers.He declined to label the U.S.-led military campaign as a "war," but made an expansive case for why he believed it was in the national interest of the United States and allies to use force.In blunt terms, Obama said the U.S.-led response had stopped Gadhafi's advances and halted a slaughter that could have shaken the stability of an entire region. Obama cast the intervention in Libya as imperative to keep Gadhafi from killing those rebelling against him and to prevent a refugee crisis that would drive Libyans into Egypt and Tunisia, two countries emerging from their own uprisings."To brush aside America's responsibility as a leader and — more profoundly — our responsibilities to our fellow human beings under such circumstances would have been a betrayal of who we are," Obama said.