The London conference is co-hosted by the British government, the United Nations and Somalia's U.N. -backed federal government, led by President Mohamed Abdullahi Mohamed, who took office in February after a Western-backed electoral process. Ethiopian Prime Minister Hailemariam Desalegn and Ugandan President Yoweri Museveni are also in attendance.
"After more than 20 years of a dramatic conflict that caused huge suffering to the Somali people. all the conditions are now met for Somalia to be a success story", said United Nations Secretary-General Antonio Guterres.
Disasters Emergency Committee CEO Saleh Saeed said: "We hope that this conference will result in much-needed progress for Somalia helping build resilience - at national, local and individual level - so that the country can withstand future humanitarian emergencies".
"Al-Shabaab has tripled its attacks on Mogadishu, and Somali forces do not yet have the capability to take over control of their own security", May said in opening remarks.
He said Somalia now hangs in the balance between peril and potential.
"This morning we presented the revised humanitarian response plan seeking an additional US$900 million to the end of the year", he said.
May said Somalia had made progress since five years ago, when al Shabaab controlled large parts of it, piracy was costing global trade $7 billion a year and the country was recovering from a starvation that killed a quarter of a million people.
World Health Organization added that if the current drought situation continues, "famine could soon be a reality".
US President Donald Trump recently approved an expanded military role in Somalia, a position that included carrying out more aggressive measures against the insurgents who hold parts of the country. Aid agencies have expressed concern that the military moves could endanger the hundreds of thousands of people displaced by the drought.
But he said it was not the time to lift the arms embargo because of fears weapons could end up in the wrong hands.
He told the delegate that Al-Shabaab can not be defeated by Somali security forces who only equipped with AK 47 which is the same weapons that al-Shabaab also poses. Save the Children chief Keven Watkins called for "decisive action" including increased help from the World Bank.
He added: "Restoring Somalia's relations with the World Bank, cancelling the country's debt, and providing immediate financial support from the World Bank's global development association facility is critical". Drought has also led to lack of clean water and the largest outbreak of cholera Somalia has seen in the last 5 years, with more than 36 000 cases and nearly 690 deaths so far in 2017 alone.