US Secretary of State Hillary Clinton has called for an end to Somalia's "hopeless, bloody conflict" and said anyone blocking recent political reforms aimed at restoring effective government should face sanctions including asset freezes.
Addressing a London conference aimed at invigorating international attempts to end two decades of anarchy, Mrs Clinton also demanded greater efforts to cut financial support for the al-Qaeda-linked al-Shabaab militant group fighting the country's weak Transitional Federal Government (TFG).
Representatives of more than 50 countries and international organisations attended the high-level event.
Al-Shabaab is the most powerful array of militias spawned by 20 years of conflict in Somalia, where armed groups have a history of wrecking attempted political settlements and perpetuating war, instability and famine.
Mrs Clinton and other speakers welcomed a 17 February agreement among Somali leaders on plans for a parliament and constituent assembly to replace the TFG when its mandate expires in August.
The TFG got a boost on the eve of the conference when the UN Security Council voted to boost by nearly half an African Union peacekeeping force in Somalia, seeking to press home a military offensive against al-Shabaab.
The resolution increasing the AMISOM force to 17,731 from 12,000 troops and police passed the council unanimously.
Mrs Clinton said al-Shabaab was weakening but pressure needed to be maintained.
British Prime Minister David Cameron told the gathering that a failure to end Somalia's chaos will endanger international security, and the time is right for the outside world to help the failed state get back on its feet.
Mr Cameron said Somalis' problems "don't just affect Somalia. They affect us all.
"In a country where there is no hope, chaos, violence and terrorism thrive. Pirates are disrupting vital trade routes and kidnapping tourists."
He announced a number of aid and development initiatives, including a proposal to set up an international taskforce on ransoms, the main tactic used by Somali pirates who seize ships and their crews in the Indian Ocean and Gulf of Aden.
Somalia collapsed into feuding between rival warlords, clans and factions after president Siad Barre was overthrown in 1991. Up to a million people have since been killed, according to the International Committee of the Red Cross (ICRC).
A conference communique said participants agreed to "act against spoilers to the peace process, and we would consider proposals" before a followup conference in Istanbul in June.
