PEACE EFFORTS:World leaders meet in LondonWorld leaders have asked Somalis to seize an "unprecedented opportunity” to rebuild their nation, at a gathering in London on the war-torn nation’s future.Ending threats of terrorism and piracy were in everyone’s interests, UK Prime Minister David Cameron said.Hillary Clinton said plans to elect leaders and adopt a constitution before August were "ambitious”.But she said the mandate of the UN-backed interim government would not be extended any longer.Somalia has endured more than two decades of civil war and famine.Representatives from many Somali factions are attending the London conference, but the Islamist group which controls much of the centre and south of the country is not invited.The UK has described Somalia as the "world’s worst failed state” but said it needs a "second chance”.Mr Cameron told the gathered leaders, who included Nigerian President Goodluck Jonathan, Ethiopian leader Meles Zenawi and UN chief Ban Ki-moon, that the world would pay a high price if it ignored the plight of Somalia."In a country where there is so little hope, where there is chaos and violence and terrorism, pirates are disrupting vital trade routes and kidnapping tourists,” he said."Young minds are being poisoned by radicalism, breeding terrorism that is threatening not just Somalia but the whole world. If the rest of us just sit back and look on, we will pay a price for doing so.”During his speech, Somalia’s President Sheikh Sharif Sheikh Ahmed called for an end to the arms embargo, saying: "We’re looking for security. We’re scared of tomorrow.”