Her assessment made clear the risk of possible military intervention as world powers consider broader steps to protect civilians and pressure the Libyan leader.

“A no-fly zone requires certain actions taken to protect the planes and the pilots, including bombing targets like the Libyan defense systems,” Clinton said.

She said discussions are going beyond specific actions toward broader authorization so countries can enforce any UN measures. No ground intervention is being considered, she told reporters in Tunis.

She said the US would support UN actions that gain a “broad base of participation, including from Arab nations,” but added that military action might be needed.

“Qaddafi must go,” Clinton said, calling him “a ruthless dictator that has no conscience and will destroy anyone or anything in his way.” “If Qaddafi does not go, he will just make trouble,” she said.  “That is just his nature.

The Security Council was scheduled to vote on a resolution to authorize a no-fly zone over Libya and stepped-up sanctions at 22:00 GMT.

The push toward action at the Security Council comes as pro-Qaddafi forces pushed forward toward the insurgent stronghold of Benghazi on Thursday and launched air raids on its outskirts.

US Undersecretary of State William Burns said Qaddafi’s forces had made “significant strides on the ground” and were now about 160 km from Benghazi.

Libyan state television said government troops had taken Zueitina, an oil port on the coastal highway 130 km from Benghazi, but the rebels said they had surrounded the pro-Qaddafi units on the approaches to the town.

Meanwhile, NATO is making contingency plans for military intervention in Libya if it is called on to do so by the UN Security Council and other North African nations, the alliance’s head said Thursday.

NATO “does not look to intervene in Libya” but wants to be prepared in case action is needed, Secretary-General Anders Fogh Rasmussen told reporters during a visit to Warsaw.

“We want to be prepared for all eventualities so we have asked our military to conduct all necessary planning so that we stand ready to assist if requested,” he said.

Fogh Rasmussen said he can’t imagine that the international community and the UN would “stand idly by” if the regime of Qaddafi continues an attack on the Libyan population that “may amount to crimes against humanity.” “I think the whole world is strongly concerned about the events in Libya. It’s absolutely outrageous to see the Libyan regime systematically attack its own civilian population,” he said.

However, he stressed that NATO would only intervene in Libya if three conditions are met — a clear need for NATO assistance, support from the region and a legal basis such as a UN Security Council resolution.