Tripoli, Libya - Leaders of Britain, France and the United States vowed on Friday to keep up their military campaign in Libya until Muammar Gadhafi leaves power, as the Libyan leader toured the streets of Tripoli.

The sunglasses of a Libyan man reflects the coffins of men who have been killed and covered with Kingdom of Libya flags at Friday prayers near the courthouse in Benghazi April15, 2011. [Photo/Agencies]

Meanwhile, Western powers struggled to stay united over a NATO-led air campaign that has so far failed to budge Gadhafi from power.

In a bid to put on a united front, however, British Prime Minister David Cameron, France's President Nicolas Sarkozy and US President Barack Obama penned a joint article dismissing a Libyan future with Gadhafi as "unthinkable" and an "unconscious betrayal" by the rest of the world.

"It is unthinkable that someone who has tried to massacre his own people can play a part in their future government," the leaders wrote.

"So long as Gadhafi is in power, NATO and its coalition partners must maintain their operations so that civilians remain protected and the pressure on the regime builds," they said.

"Then a genuine transition from dictatorship to an inclusive constitutional process can really begin, led by a new generation of leaders. For that transition to succeed, Colonel Gadhafi must go, and go for good."

Reaction to the letter from the Gadhafi camp was swift as the Libyan leader's daughter Aisha told a rally in Tripoli, at a family compound bombed by the US in 1986, that demanding her father's departure was an insult to the Libyan people.

"Talk about Gadhafi stepping down is an insult to all Libyans because Gadhafi is not in Libya, but in the hearts of all Libyans," she said in a speech broadcast live on Libyan television to mark the 25th anniversary of American strikes on the huge complex, which includes military barracks.

Earlier in the day, her father had toured the streets of the capital in an open-top vehicle, wearing sunglasses and a hunting hat and hailing bystanders with clenched fists.

"God, Libya, Muammar and no one else," supporters chanted as loud explosions rocked the Bab al-Aziziya neighborhood home to Gadhafi's residence and a base for most foreign journalists in the capital.

Cracks opened up in NATO as Washington rebuffed French appeals for more assistance with the enforcement of the United Nations Security Council resolution authorizing all necessary means to protect Libyan civilians.

French Foreign Minister Alain Juppe made a personal appeal to US Secretary of State Hillary Clinton for Washington to resume major air raids in Libya, but he said his plea was rebuffed.

"I told her we needed them back, we would have liked them to return," Juppe said, adding that Clinton said US planes would continue to fly on a case-by-case basis.

At an international conference hosted by the Arab League in Cairo, UN chief Ban Ki-moon called for a "political" solution and immediate cease-fire, while European Union foreign policy chief Catherine Ashton urged Gadhafi to resign immediately.

A NATO declaration said that the allies "strongly endorse" calls for Gadhafi to leave power.

Alliance foreign ministers played down any rift after France and Britain pressed allies to contribute more combat jets to the mission and intensify the raids against regime tanks and artillery.

However, differences remained over the air raids, which are being conducted by just six of the 28 allies, against forces threatening the population. Rebels have urged NATO to step up the air campaign as the mission has failed to shift the balance of power so far.

Reuters - AFP