Morgan Tsvangirai told The Associated Press he would meet with President Robert Mugabe later on Saturday to discuss the arrest of Roy Bennett, who was due to be inaugurated as deputy minister of agriculture in the coming week.
Bennett was detained by police on Friday while Tsvangirai and Mugabe were presiding over the inauguration of senior Cabinet ministers.
Bennett’s arrest illustrates the deep gulf of mistrust Mugabe’s Zanu-PF party and Tsvangirai’s Movement for Democratic Change must bridge.
A pro-Mugabe newspaper reported on Saturday that Bennett was arrested because of an alleged plot from 2006 to overthrow Mugabe, resurrecting a long-discredited claim.
The arrest was a test for Tsvangirai, who had hesitated to join the government for fear he would be in the position of having to answer increasingly desperate calls by Zimbabweans for help, with little power to affect change.
Bennett’s "safety was guaranteed by the South African and Zimbabwean governments", Tsvangirai said on Saturday.
"His arrest … raises a lot of concerns.
"It undermines the spirit of our agreement. It is very important to maintain the momentum of our agreement."
But Tsvangirai called for patience: "I must say, we have to budget for some residual resistance from those who see this deal as a threat to their interest."
Tsvangirai did not specify, but there long has been speculation Mugabe was under pressure from aides in the military and government who don’t want to give up power and prestige to their rivals.
Tsvangirai said he believed the coalition Cabinet could make progress together, and called his relationship with Mugabe a "working arrangement".
"But obviously with our history we cannot immediately say we are the best of friends," he said. "As you begin to trust, the walls will start falling down."
Tsvangirai expressed frustration that resistance to the agreement was distracting the new government from the monumental tasks of rebuilding the country.
It has the world’s highest inflation rate, a hunger crisis that has left most of the population dependent on foreign handouts, and a cholera epidemic that has killed more than 3 500 people since August.
"We should be talking about feeding the people," Tsvangirai said.
"Our motivation is to get the civil servants back to work and the schools and the hospitals back to serving the people.
"There’s no way we will neglect our obligation, even though there are signs of resistance."