Hague arrived Thursday in Somalia to open the British Embassy for the first time since it was evacuated in 1991.
Somalia last year established a functioning central administration for the first time since the 1990s. It's struggled to extend its authority beyond Mogadishu, however, because of separatist threats from al-Shabaab, a militant group aligned with al-Qaida.
Al-Shabaab claimed responsibility for an April bombing of a courthouse in Mogadishu. The U.N. High Commissioner for Human Rights estimates more than 50 civilians were killed in the attack.
"Somalia has been through a dramatic shift over the last year but continues to face huge challenges," Hague said in a statement. "We should be under no illusions as to the sustained efforts that will be required, in Somalia and from its international partners, to ensure that Somalia continues to make progress."
Somali Foreign Minister Fawzia Yusuf Adam said last month "the road to full recovery will be long."
An international meeting on Somalia is to convene in May in London.