Somali President Hassan Sheikh Mohamud told a London conference this week his country has made fundamental gains, though he was worried militant group al-Shabaab was on the cusp of "a new phase of insurgency and a campaign of terror."
Somalia last year formed a functioning central government for the first time since the 1990s. Despite retaking territory from al-Shabaab last year, the government has struggled to expand its authority beyond Mogadishu.
Eliasson said the Somali government needs support from the international community despite the recent gains.
"(Mohamud's) challenge is to establish authority in all of Somalia and I think it's important for the international community to support this desire to create a well-functioning federal state," he said in a statement.
The British government said it was committed to provide $54 million to help Somalia address its political challenges. Another $300 million was raised for the Somali security sector.