Nato chief Anders Fogh Rasmussen urged the UN Security Council to quickly agree a resolution on Libya on Thursday, warning "time is running out" to stop Muammar Gaddafi from prevailing.
"If Gaddafi prevails it will send a clear signal that violence pays. That would be unacceptable from a humanitarian and democratic perspective," Rasmussen said on his facebook page.
"But time is running out. The sooner the United Nations can reach an agreement the better," he said.
"Nato stands ready to protect the civilian population if there is a demonstrable need, clear legal basis and strong regional support."
France, Britain and the United States are pressing for a UN Security Council vote Thursday on a resolution that includes a no-fly zone to prevent Gaddafi from using his air force to bomb rebels.