Zimbabwe President Robert Mugabe promised to cooperate fully with the newly appointed Prime Minister Morgan Tsvangirai under their new unity government.

"I offer my hand of friendship and cooperation, warm cooperation and solidarity in the service of our great country Zimbabwe," Mugabe said in a speech after Tsvangirai's swearing-in.

"If yesterday we were adversaries... today we stand in unity. It's a victory for Zimbabwe," he said.

"We have shown that we have the capacity to resolve our differences through negotiation and compromise. We must build on this unity by turning our swords into ploughshares.

"We are all aware that the road has been long, tedious and often frustrating. It's has not been easy to overcome the deep-seated mistrust," he said.

"This was made worse by our detractors who sought to overturn the process using overt and covert means," Mugabe added.

The 84-year-old president has often accused Western powers, particularly former colonial power Britain, of trying overthrow his government and frustrate the unity talks.

AFP