* Somalia striving to emerge from 20 years of war
* Puntland says centre rejects federal structure of state
* Reversal of political gains could benefit Islamist rebels
MOGADISHU, Aug 5 (Reuters) - Somalia's semi-autonomous Puntland region said on Monday it had cut all ties with the central government in a likely setback to efforts to pacify the Horn of Africa Country as it emerges from two decades of conflict.
Puntland accused the Mogadishu government of refusing to share power and foreign aid with the regions in line with the country's federal structure, as well as taking its eye off the fight against al Qaeda-linked Islamist militants.
"The fragmented country has been plunged back into a vicious cycle of violence, displacement, clan animosities and a complete disregard for the country's genuine Provisional Federal Constitution," Puntland's administration said in an official statement.
"Puntland hereby suspends all cooperation and relations with (the) Federal Government of Somalia."
The election in September of President Hassan Sheikh Mohamud, a political newcomer with a background in reconciling clan feuds, was seen as a vote for change.
But he has struggled to overcome acrimonious clan politics, corruption and a stubborn Islamist insurgency. Somalia's neighbours and foreign powers fear a return to civil war in a country long seen as a launchpad for militant Islam.
Mohamud's cash-strapped federal government exerts little authority beyond the capital. How to divvy up power between the centre and regions is a thorny issue that the provisional constitution failed to address.
In a country where clan loyalties rather than ideology determine political support and access to resources, analysts say Mogadishu is reluctant to hand power to the provinces fearing a break up of the state. Meanwhile the regions are demanding more autonomy.
Puntland's move raises the prospect of other regions following suit, in particular Jubaland in the far south where dozens of civilians have been killed in recent fighting between two rival warlords who claim control.
Puntland said it would only resume normal relations with Mogadishu when the central government respected the country's federal structure. There was no immediate response from the federal government.
Puntland has largely avoided being caught up in successive Islamist insurgencies although its shores have been a haven for pirates. But al Shabaab rebels, squeezed out of their redoubts in southern and central Somalia by African peacekeepers, have slowly infiltrated Puntland, regional officials say.
Somaliland, on Somalia's northwestern tip, declared itself independent in 1991 shortly after civil war erupted, but it is not an internationally recognised as a sovereign state. (Editing by Richard Lough; Editing by Michael Roddy)