Under the deal signed on September 15, Mugabe would remain as president while Morgan Tsvangirai, the MDC leader, would take the new post of prime minister. It also entailed a sharing of ministries among the Zanu-PF, the MDC and another splinter opposition group.
But the agreement soon ran into trouble with Mugabe usurping most of the ministries for his own men.
The parliament also needs to approve an amendment to create the office of the prime minister and define its powers.
Khupe said that MDC would not join the government until the amendment was passed and other outstanding issues - including the appointment of provincial governors - were resolved.
She also criticised the leaders of the Southern African Development Community (Sadc) regional bloc for insisting that Zimbabwe form a unity government immediately.
The SADC summit last Sunday in the Johannesburg called for resolving the conflict between Mugabe and Tsvangirai by appointing joint ministers to share control of home affairs, which runs the police.
"Our issues were not addressed by Sadc," Khupe said.
"All our issues were glossed over and narrowed down to the issue of the home affairs ministry," she added.
"[But] we are committed and we remain committed to this dialogue," she said.