Speaking at the state funeral of a former guerrilla leader who fought for independence from Britain in 1980, Mr Mugabe, referring to Mr Tsvangirai’s temporary withdrawal from the cabinet, said: “Even if some person is not mentally stable he is still your partner.

“We bound ourselves to work together even though we had disparate positions. We will continue talking, no matter what,” Mr Mugabe told mourners at the Heroes Acre cemetery west of the capital as Mischek Chando was buried.

Mr Mugabe said his Zanu-PF party and Mr Tsvangirai’s Movement for Democratic Change had taken “positive steps” despite having faced difficulties. “There can be disagreement but that’s ours to handle,” he said. “On an odd day, one party decides it should not be fully in the process. It has one leg in and one leg out and you begin to wonder if you are with people who know what agreement means,” he added.

Mr Tsvangirai said it was Mr Mugabe, in power since independence and seen as increasingly autocratic, who has failed to live up to their power-sharing agreement. He withdrew from cabinet on October 16, accusing Mr Mugabe of trampling on human rights, and said he would only return when confidence in the unity government was restored.

On Friday, foreign ministers from Mozambique, Swaziland and Zambia – members of the Southern African Development Community that pushed Mr Mugabe and Mr Tsvangirai to share power – met separately with the two. After the meetings, they said they would recommend to their heads of state that a summit be convened, a move for which Mr Tsvangirai has pushed. They did not say where or when. At a meeting in Berlin on Monday, key international donors urged Zimbabwe’s factions to end the current crisis and echoed some of the concerns raised by Tsvangirai.

Mr Tsvangirai’s party has reported a recent surge in political violence, allegations that Mr Mugabe’s party denies. The barring on Thursday of UN torture investigator Manfred Nowak raised more questions about how much power Mr Tsvangirai can wield in the face of fierce opposition.

Mr Tsvangirai had invited Nowak but the envoy was stopped at the airport. Zimbabwe’s Foreign Minister Simbarashe Mumbengegwi, a Zanu-PF leader, called Mr Nowak’s attempted visit “a provocation of the highest order”.