Rome is negotiating an African haven for the Libyan leader as international pressure mounts on him to go

Efforts appear to be under way to offer Muammar Gaddafi a way of escape from Libya, with Italy saying it was trying to organise an African haven for him, and the US signalling it would not try to stop the dictator from fleeing.

The move came amid mounting diplomatic and military pressure on Gaddafi as Britain tries to assemble a global consensus demanding he surrender power while intensifying air strikes against his forces. An international conference in London – including the UN, Arab states, the African Union, and more than 40 foreign ministers – will focus on co-ordinating assistance in the face of a possible humanitarian disaster and building a unified international front in condemnation of the Gaddafi regime and in support of Nato-led military action in Libya.

On the eve of the conference, Italy offered to broker a ceasefire deal in Libya, involving asylum for Gaddafi in an African country. "Gaddafi must understand that it would be an act of courage to say: 'I understand that I have to go'," said the Italian foreign minister, Franco Frattini. "We hope that the African Union can find a valid proposal."

A senior American official signalled that a solution in which Gaddafi flees to a country beyond the reach of the international criminal court (ICC), which is investigating war crimes charges against him, would be acceptable to Washington, pointing out that Barack Obama had repeatedly called on Gaddafi to leave.

"I can't say I know of active efforts to find him a place to go, but I would not say it has been ruled out," the official said. "The ICC has said it will ready to pursue the case, but there are also the rules of the ICC," he added, pointing out that some countries do not recognise the court's jurisdiction.

British officials said they would rather see Gaddafi face trial, but if his escape was the price of a peaceful settlement they would be able to live with that.

David Cameron and Nicolas Sarkozy tried to ratchet up the pressure on Gaddafi, issuing a joint statement on the eve of the conference declaring his era over, and indicating that his lieutenants might escape prosecution if they abandoned him immediately. "We call on all his followers to leave him before it is too late," they said.

Meanwhile Obama gave a televised speech to the American people in which he explained why the US was involved in the conflict, as a response to his domestic critics over the crisis. The US president increased the pressure on Gaddafi by saying it was imperative his rule be ended. "We continue to pursue the broader goal of a Libya that belongs not to a dictator but to its people," he said. "Gaddafi has not yet stepped down from power and until he does Libya will remain dangerous."

He also used his speech to emphasise that strikes against Gaddafi's forces would continue even as American leadership of the campaign transferred to Nato tomorrow. "Our coalition will keep the pressure on Gaddafi's forces," he said.

Meanwhile, with the Libyan regime's forces and rebels squared for a battle around Gaddafi's birthplace of Sirte, British planes taking part in the coalition campaign stepped up their bombardment.

RAF Tornados hit 22 tanks, armoured vehicles and artillery pieces over the weekend, the Ministry of Defence said. Early Monday, they struck ammunition bunkers near Subha in southern Libya, according to Major General John Lorimer, the MoD's chief military spokesman. Defence officials said the higher tempo was the result of more intelligence surveillance and assessments from reconnaissance aircraft.

Discord over the air strikes threatens to undermine the consensus the UK will attempt to construct at the Lancaster House conference. Russia denounced the air campaign, arguing it violated UN security council resolution 1973, which permitted "all necessary measures" to protect civilians. Foreign minister Sergei Lavrov said: "We consider that intervention by the coalition in what is essentially an internal civil war is not sanctioned."

Turkey's prime minister, Recep Tayyip Erdogan, was also critical, and in a symbolic blow to the London conference, it emerged that Amr Moussa, the secretary general of the Arab League – whose support for military action was deemed crucial by Washington and its allies – would not be attending, sending a deputy instead.

The joint statement issued by Cameron and the French president was intended in part to heal discord over the command of the air campaign and France's recognition of the Benghazi-based National Libyan Council. The rebels are not invited to the conference, but William Hague is expected to meet one of their leaders, Mahmoud Jibril. The shadow defence secretary, Jim Murphy, will warn today: "The bravery of the Libyan opposition is not in doubt. What is unclear is the motives of some, other than the removal of Gaddafi. As the opposition move westwards across Libya it is crucial that we better understand who they are and their wider ambitions."