David Cameron and Barack Obama have urged the Libyan leader to stand down, saying they would "turn up the heat on the Gaddafi regime".
The two men have held a news conference in London after discussions at Downing Street.
The US President said: "We will continue to strongly oppose the use of violence against protesters and any efforts to silence those who yearn for freedom and dignity and basic human rights - that's one of the reasons we are working together in Libya alongside our Nato allies and partners to protect the Libyan people.
"We will continue those operations until Gaddafi's attacks on civilians cease. Time is working against Gaddafi and he must step down from power and leave Libya to the Libyan people."
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