The MDC leader accused Mr Mugabe of trying to secure all key ministry posts for his ruling Zanu-PF party.
The MDC has reportedly said if Zanu-PF gets defence, then home affairs – which covers policing – must go to the MDC.
The two bitter rival parties agreed to share power on 15 September but have been deadlocked over cabinet posts.
Former South African President Thabo Mbeki is expected in the Zimbabwean capital, Harare, on Monday in an attempt to break the impasse over the appointment of cabinet posts.
AFP news agency quoted Mr Tsvangirai as telling a rally in Harare on Sunday: "If they [Zanu-PF] do it that way, we have no right to be part of such an arrangement.
"The people have suffered. But if it means suffering the more in order for them to get what is at stake, then so be it.
"We will renegotiate until an agreement is reached but that does not mean we will compromise for the sake of it."
Mr Tsvangirai’s warning follows news on Saturday that Mr Mugabe had allocated key ministries to his own party – in violation of the deal.
MDC spokesman Nelson Chamisa said this was "Zanu-PF’s arrogant wish list" and warned it was putting the deal in jeopardy.
Edwin Mushoriwa, spokesperson for the breakaway MDC faction led by Arthur Mutambara that also signed the September 15 deal, condemned the move as "hallucination on the part of Zanu-PF."
"That list is what they wish to happen. It was not agreed on. As far as we know, there was no agreement on the allocation of cabinet posts," he said.
Under the existing agreement Mr Mugabe remains president while Mr Tsvangirai becomes prime minister.
The continuing political impasse is not thought to have helped ease the country’s crippling economic crisis.
On Thursday, it was announced that Zimbabwe’s annual inflation rate had soared to 231,000,000%.