The NATO chief said he was confident that time was running out for Libyan leader Muammar Gaddafi, despite the prolonged stalemate between his forces and rebels who seek his ouster.
But Anders Fogh Rasmussen also acknowledged the brutal war that has raged for nearly two months would be resolved politically, not militarily.
"The game is over for Gaddafi. He should realize sooner rather than later that there's no future for him or his regime," the NATO secretary-general told CNN's "State of the Union" program.
"We have stopped Gaddafi in his tracks. His time is running out. He's more and more isolated."
Given the "wind of change" sweeping across North Africa and the Middle East, the death of Al-Qaeda leader Osama Bin Laden and the growing pressure on the Taliban in Afghanistan, the Danish former prime minister said he was "very optimistic" that Gaddafi would ultimately lose his decades-old grip on power.
NATO forces have kept up an air bombing campaign against Libyan military targets since March, but have failed so far to prevent Gaddafi from killing scores of his own people in rebel-held towns and cities -- the stated goal of a UN resolution authorizing the allied mission.
"First of all, we have to realize that there is no military solution. We will need a political solution" to break the stalemate, said Rasmussen.
But he also recognized it was "hard to imagine the attacks, the outrageous and systematic attacks against Libyan people, will stop as long as Gaddafi remains in power."
The United States led the bombing campaign in its first week but has since relinquished lead operational control to the transatlantic military alliance. US President Barack Obama has also called for Gaddafi to relinquish power.
His national security adviser, Tom Donilon, said Washington has no plans for now to step up its involvement in Libya.
"NATO is still running this operation now, we're supporting it," Donilon told ABC television's "This Week."
"They have the assets that are needed for them to engage in the civilian protection mission, and they are engaging."
Asked whether the United States would take the lead once more in allied operations in Libya, Donilon simply answered "no."
"The future belongs to the Libyan people, and it's for the Libyan people to decide the future of the country. We are there to protect civilians against any attack according to the UN Security Council mandate, and we will stay as long as necessary to fulfill that mandate," he added.
Former vice president Dick Cheney, meanwhile, criticized the Obama administration's "confused" policy on Libya.
"It's not clear exactly what the policy is," he told "Fox News Sunday."
"The idea that you can turn something that important over to NATO and have NATO deal with Libya and support our interests there doesn't work very well... It's unfortunate we haven't been more forthright and more forceful in terms of our approach."
He said the Obama administration should have engaged in a real military effort to rid Libya of Gaddafi.
"It's not enough to simply sit on the sidelines and say get rid of Gaddafi," Cheney said. "It looks as though the policy of the administration has been is to hope for Gaddafi's departure but not be prepared to do enough to make sure it happens."
