The United Nations Security Council says Somalia's transition is at a “decisive phase” and must be completed by August 20.

In a statement Wednesday, the Council urged all parties involved in a U.N.-backed roadmap to a permanent government to follow through on their commitments.

The statement came as a nine-day conference began in the Somali capital, Mogadishu, where an 825-member assembly is expected to ratify a new constitution.

The gathering had been postponed three times this month.

The assembly includes a broad range of regional delegates who will discuss and possibly amend a draft measure. They will likely provisionally adopt the constitution.

Somali President Sheikh Sharif Sheikh Ahmed says the gathering marks a historic moment for the country.

“I would like to congratulate all Somalis on this success at this crucial time. We are here today to approve the constitution, which means the foundation of our country's governance is being laid down.”

Somalia's Transitional Federal Government has been in place since 2004. It has been unable to assert power because of chronic infighting and chaos in the country.