NATO is reportedly delaying its planned takeover of military command in Libya as U.S. Ambassador to the United Nations Susan Rice says the Obama administration has not ruled out arming Libyan rebels in their fight against Muammar al-Qaddafi. "We have not made that decision, but we've not certainly ruled that out," she said on ABC's "Good Morning America." Rice also reiterated the the principal goal is to protect civilians and establish a no-fly zone. This comes as Libyan government tanks and rockets blunted a rebel assault on Qaddafi's hometown of Sirte on Tuesday and drove back the ragtag army of irregulars, even as world leaders prepared to debate the country future in London. Rockets and tank fire sent Libya's rebel volunteers in a panicked scramble away from the front lines, suggesting that the opposition is still no match for the superior firepower and organization of Qaddafi's forces, despite an international campaign of deadly airstrikes. A U.N.-mandated no-fly zone and campaign of strikes by the U.S. and its allies helped rebel forces regain territory lost of the past week, when they were on the brink of defeat by government forces.