JOIN USAsked about remarks by British counterpart Liam Fox suggesting targeting Gaddafi himself, Gates said the allied operation should stick to the parameters as authorized by the UN Security Council.
"I think that it's important that we operate within the mandate of the UN Security Council resolution," he said.
Gates, who was speaking on a US military plane en route to Russia, said the intervention was backed by "a very diverse coalition" and warned that expanding its goals could complicate the consensus around the UN resolution.
"If we start adding additional objectives then I think we create a problem in that respect," he said. "I also think it's unwise to set as specific goals things that you may or may not be able to achieve."
He also expressed caution about providing direct support to rebel forces and referred to a long term "process" that could see Gaddafi toppled.
"I think this is basically going to have to be resolved by the Libyans themselves," he said. "Whether or not there is additional outside help for the rebels I think remains to be seen."
Initially, the goal was to shut down Gaddafi's air force to safeguard civilians, he said.
"The key is to first of all, establish the no-fly zone, to prevent him from using his military forces to slaughter his own people," he said.
Asked about criticism about the air strikes from the head of the Arab League Amr Mussa, Gates said he was reassured by renewed support for the operation by the bloc.
"I saw on the news just before I got on the plane that in fact the Arab League voted had again to reassert its support. So I think we're OK," he said.
Gates said governments were discussing how best to organize the military command of the operation, with Arab states reluctant to have a NATO flag over the intervention.