Somalia's transitional cabinet has extended its term by an extra year saying it wants to ensure continuity in its fight against insurgents, joining the country's parliament in lengthening its mandate.

The cabinet decision comes at a time the country's president and parliament speaker wrangle over a unilateral decision by the Transitional Federal Government's Parliament to extend its term by three more years, taken in February, drawing international condemnation.

The US and Britain both criticised the Somali parliament for extending its term and the United Nations called it disappointing, but the parliament speaker said last week the assembly would not change its decision.

The cabinet decided to prolong its life after it "discussed the current situation ... especially the political, security and the ongoing operations of the restoration of the peace," it said in a statement late on Sunday.

Under the terms of a 2009 deal, the Somali government and parliament's mandate is set to expire on August 20 this year, by which time they were supposed to have enacted a new constitution and held elections.

"The proposed election on August has to be suspended up to August 2012 so as to carry out and conclude the necessary reforms and duties of transitional period including the formation of strong Somali national forces, restoration of peace ... good governance, public infrastructure, reconciliation and to fight the corruption."

Somalia has not had an effective central government since the 1991 overthrow of dictator Mohamed Siad Barre. First clan warlords and now Islamist insurgents mean the government controls little more than the capital Mogadishu.