"The substantial role that the United States played at the beginning, because of its unique capacities, has ended, the transition has taken place, in days, not weeks," White House Press Secretary Jay Carney told reporters at his daily news conference.
"The (US) President pledged to the American people at the start of our effort in Libya that US military action would be limited in duration and scope, and that we would ultimately transition from a US to a coalition lead in days and not weeks," Carney said.
The alliance effort, dubbed ''Operation Unified Protector'', has assets in place and is now leading efforts to enforce the arms embargo and the no-fly zone, and to protect Libyan civilians, he said.
Carney said the lead role that the US took at the beginning to create conditions under which a no-fly zone could be enforced effectively and also to take measures very quickly that would protect Libyans was very limited in duration, and the transition has now taken place.
"The President believes that the mission itself will be limited in duration, but of course we don''t have crystal balls and we cannot predict when it will end. And it is obviously also part of a coalition effort that the United States is engaged in," he said.
He exuded confidence that the Libyan people will be able to decide their future and that US and its partners would be taking measures, separate from the military mission to put the kind of pressure on Gaddafi that needs to be placed on him to isolate him, to help bring him to the conclusion that he can no longer stay in power and he needs to step aside for the good of his people and Libya''s future.
Referring to the defection of Libyan Foreign Minister Moussa Koussa, he termed this as the most important event in the last 24 hours.
"If there was ever a sign that the sort of inner circle surrounding Muammar Gaddafi was crumbling, it was the defection of Moussa Koussa to the United Kingdom. So we believe that the pressure is obviously having an effect, and we will keep it up with our partners," he added.