In a joint declaration, President Barack Obama, British Prime Minister David Cameron and French President Nicolas Sarkozy say they will not stop the campaign and will "remain united." Writing in a newspaper opinion piece, the three leaders said their mandate under a United Nations Security Council resolution is to protect civilians in Libya.
"It is not to remove Gadhafi by force," they wrote. The declaration will be published in Friday's editions of the International Herald Tribune, Le Figaro and the Times of London.
The joint piece comes as French and British officials have been calling for more strikes by their NATO allies against Gadhafi forces.
The carefully worded declaration denounces Gadhafi and says: "It is impossible to imagine a future for Libya with Gadhafi in power."
"So long as Gadhafi is in power, NATO must maintain its operations so that civilians remain protected and the pressure on the regime builds," the three leaders wrote. "Then a genuine transition from dictatorship to an inclusive constitutional process can really begin, led by a new generation of leaders. In order for that transition to succeed, Gadhafi must go and go for good.
They say Gadhafi must leave "definitively." If he doesn't, they warn, his opponents would face vicious reprisals and the country could become a haven for extremists.
White House spokesman Jay Carney on Thursday played down differences among the allies. Asked about British and French demands for more strikes, Carney said: "It is my understanding that that tempo has picked up. ... We remain confident that NATO is fully capable of executing the mission."