World leaders are gathering in London Thursday for a conference aimed at coming up with a coordinated response to decades of instability in Somalia.

Representatives of 40 countries will attend the conference, including U.S. Secretary of State Hillary Clinton and United Nations Secretary-General Ban Ki-moon.

Leaders at the one-day conference will try to pull together international support for Somalia, which has endured two decades of civil war and poverty since the fall of its last stable government in 1991.

The country's weak Western-backed transitional government has recently struggled to deal with a devastating famine, as well as pirates and Islamist rebels that are seen as a threat to regional security.

Ahead of the conference, Somali Prime Minister Abdiweli Mohamed Ali warned that his country is at a crossroads, and that failure to address its problems would have global ramifications.

“The problems of Somalia – such as piracy, terrorism, anarchy, refugees, famine, droughts – are not unique to Somalia and will not be confined to the borders of Somalia. So we have to all hope to contribute and succeed.”

Somali's government has been involved in a four-year battle with al-Qaida-linked insurgent group al-Shabab, which controls large portions of the country.

Al-Shabab suffered a major defeat on Wednesday when it was forced to retreat from Baidoa, Somalia's third largest city that has long been considered a rebel stronghold.

Somalia's transitional government also got a boost from the United Nations on Wednesday. The Security Council agreed to expand the African Union Mission in Somalia (AMISOM) by nearly 6,000 troops.

Ethiopia, Kenya and the African Union all have contributed soldiers to the fight against al-Shabab, which aims to impose its strict version of Islamic law across Somalia.

Thursday's conference will also focus on the establishment of a permanent Somali government after the transitional period ends in August.

The current international plan calls for a new government to be appointed within six months. But critics warn the government may not enjoy much legitimacy unless a new constitution is formed and elections are held in the war-ravaged country.