Speaking at the funeral of one of his party's senate members, Mugabe said the MDC has "one leg in, and one leg out" of the government.
"The requirement is that we indeed continue step-by-step to move together and whatever are the difficulties, become our difficulties together," he said.
"For one party ... to decide 'We shall not be fully in the process' ... then you begin to wonder whether you went into the agreement with persons who actually appreciated what going into an agreement means."
State media also reported on Saturday that Mugabe called Tsvangirai "dishonest".
"They can never be true and genuine partners and they have proved to be dishonest," he said.
"We, however, want to assure you that we will not allow the situation to continue like that."
Mugabe's comments came as negotiators from the Southern African Development Community (Sadc) proposed an emergency summit to resolve the crisis.
Sadc, a 15-member bloc, has been involved in a search for a solution to Zimbabwe's governance problems.
Ministers from Mozambique, Swaziland and Zambia, support staff from the Sadc secretariat and representatives of Thabo Mbeki, a Sadc mediator and former South African president, have been meeting Zimbabwean officials over the past two days.
It was not immediately clear how the negotiations progressed, but analysts said there were slim chances of a breakthrough as the Zanu-PF and the MDC remain at loggerheads over some aspects of their power-sharing pact.
The MDC says Zanu-PF has blocked the swearing-in of some of its officials.
Zanu-PF and the MDC signed a power-sharing deal in September last year after a crisis that followed disputed elections and political violence.