WASHINGTON- US and allied forces have effectively established a no-fly zone over Libya and halted an offensive by Colonel Muammar Gaddafi against rebels in Benghazi, the top US military officer has said. Admiral Mike Mullen, the chairman of the US Joint Chiefs of Staff, told NBC's Meet the Press programme on Sunday that the US-led air strikes that began on Saturday "took out" Gaddafi's air defences, struck air fields and attacked Libyan ground forces near the eastern rebel stronghold of Benghazi. "He [Gaddafi] hasn't had aircraft or helicopters flying the last couple days. So effectively that no-fly zone has been put in place," Mullen said. "We have halted him in the vicinity of Benghazi, which is where he was most recently on the march," he said. The US military also used B-2 stealth bombers, according to US media reports. Mullen emphasised that Western military operations were narrowly focused on protecting civilians and aiding humanitarian efforts under a UN Security Council resolution, not on ending Gaddafi's 41-year rule. "What we expect is [for] him to stay down, not fly his aircraft, not attack his own people and to allow the humanitarian efforts ... to take place," Mullen said. In the next few days, Mullen said, the United States expects to relinquish its leadership of the Libyan operation, dubbed ‘Odyssey Dawn', which also currently includes Britain, France, Canada and Italy. But he did not say who would assume the lead.