PM ends boycott of unity cabinet, saying he will give it time to resolve difficulties.
Bennett was arrested in February on charges of possessing weapons with an intention to commit sabotage, terrorism, banditry and insurgency.
The case dates back to 2006, when a weapons dealer was arrested and initially accused of plotting to assassinate Robert Mugabe, the president.
“You have to look at the emotional history of this country”
Chris Mutsvangwa, Zimbabwean political analyst
The dealer has said that police tortured and forced him to make a false confession implicating several people from both Mugabe’s party and Tsvangirai’s party, including Bennett, in the alleged plot.
The dealer, who eventually was cleared of treason but charged of possessing illegal weapons, is a key witness in Bennett’s trial.
Morgan Tsvangirai, the president, says the charges have been fabricated in order to keep Bennett, a senior member of the Movement for Democratic Change (MDC), out of Zimbabwe’s unity government.
Bennett is poised to become Zimbabwe’s deputy minister of agriculture, but Mugabe refuses to swear him in until he is proven innocent of all charges, some of which carry a possible death penalty.
Haru Mutasa, Al Jazeera’s correspondent in the Zimbabwean capital, Harare, said the trial would test a new deal brokered by the regional leaders.
Zimbabwe’s political rivals held talks last week in Mozambique in an effort to ease tensions within the unity government.
Former rivals, Mugabe and Tsvangirai came together last year to form the unity government.
But Mugabe says he will not give into any more demands until targeted sanctions on him and his close allies are removed by Western countries.
Bennett, who served as a policeman under the Rhodesian Forces during Zimbabwe’s liberation war, was one of 4,000 commercial farmers who fought to keep land that he eventually lost during a land redistribution programme initiated by Mugabe in 2000.
In 2004, he was sentenced to 12 months in jail after he was convicted of assaulting a minister from Mugabe’s Zimbabwe African National Union-Patriotic Front (Zanu-PF) party during a parliamentary debate.
He returned to Zimbabwe in early 2009 after spending two years in exile in South Africa.
Chris Mutsvangwa, a Zimbabwean political analyst, told Al Jazeera: “You have to look at the emotional history of this country amongst the many possible candidates which the MDC can have, Bennett tends to exert a lot of controversy.
“These are legitimate controversies on the part of us who fought in the liberation war – that a man who was our adversary at that time now becomes a minister of agriculture in a party which was part of the GNU [Government of National Unity].”