In an interview with The Associated Press, Morgan Tsvangirai also said he believes the international community will rally to help end Zimbabwe's political and economic crisis, which has spawned hyperinflation and sent thousands fleeing to neighboring South Africa every day.
Mugabe ceded some power in Zimbabwe for the first time in 28 years, signing a power-sharing deal with Tsvangirai and a leader of a splinter opposition faction Monday.
"The deal as far as we are concerned is the best thing for the country," Tsvangirai said at his home in the capital. "We will be able to work within the deal to achieve the necessary transformation."
Meeting with reporters for his first interviews since signing the deal, the 56-year-old Tsvangirai looked confident but tired as he spoke about the hard work ahead.
Under the pact, already criticized by other opposition leaders, Mugabe remains president and head of government, chairing the Cabinet. Tsvangirai will be prime minister and head of a new Council of Ministers responsible for forming government policy. He is deputy chairman of Cabinet.
The new government is expected to be sworn in this week.
Long-simmering, bitter differences and the nation's economic collapse - inflation is officially running at 11 million percent - put the deal under intense pressure.
Tsvangirai was asked if he trusted Mugabe.
"Ask me a generic question and I say 'No' because of the experience I have had with him," he responded. "(But) I trust he is committed to this agreement, I trust he wants this deal as much as we do. He wants to move forward because it is part of his legacy."
In the decade that he has opposed Mugabe, Tsvangirai has been tortured, detained repeatedly and went through a treason trial with a possible death sentence.
On the windowsill in his home office a sign reads: "I wish a long life to my enemies so they may see all my successes."
Tsvangirai said the support of international community as well as financial institutions such as the World Bank and the International Monetary Fund is "essential for creating international confidence."
"This is the beginning of building the necessary confidence for investment and aid. We are confident that we will be able to lay the groundwork for encouraging people (investors and aid agencies) to come to the country," he said.
Wary Western leaders say they are waiting for the new government to prove its commitment to democracy.
U.S. Ambassador James McGee told the AP the United States is adopting a "very careful wait-and-see stance" about the power-sharing agreement.
"If this works out the way Mr. Tsvangirai hopes it will, we will be very willing to work with the people of Zimbabwe," McGee said.
He said Washington is committed to doing what Tsvangirai has requested - "taking care of food insecurity problems" of Zimbabwe's people.
The International Red Cross estimates more than 2 million people are hungry in Zimbabwe, and that the number is going to rise to 5 million, about half the population, by year's end.
"We will step forward, we have food in country, in the region and food on the high seas destined for Zimbabwe," the U.S. envoy said.
McGee added that Zimbabwe's new government needed to ensure that nongovernment organizations have access so they can deliver the food. Only last week, Mugabe lifted a monthslong ban on organizations delivering food aid after accusing them of favoring the opposition.
Besides getting food to hungry Zimbabweans, Tsvangirai said his priorities are to build a more democratic society and free the media. State abuse of power "has to go," he said.
The deal has been criticized privately by some in the opposition who are unhappy that it gives Mugabe too much power. They fear he will exploit that, especially by playing on tensions between the two opposition groups.
Also critical is the Zimbabwe Congress of Trade Unions, which brought Tsvangirai to prominence. It said the agreement had been negotiated only by politicians without input from civil society, that it did not respect the March presidential election in which Tsvangirai and his party won more votes than Mugabe, and did not provide for a transitional government to organize new elections.
The agreement provides for a new constitution to be drawn up and a referendum on it to be held within two years.
Tsvangirai tried to allay fears that the agreement will bring government paralysis.
"It is work in progress. It has not dawned on people how much hard work there is to do," he said.
The agreement provides for 31 ministers - 15 nominated by Mugabe's party, 13 by Tsvangirai and three by Arthur Mutambara, leader of a smaller opposition faction.
Parties have started talks on allocating Cabinet posts. Tsvangirai said the matter would be resolved by Wednesday.
Opposition leaders want the Home Affairs Ministry that would give them charge of the police who have terrorized them and their supporters this year, and Mugabe would retain the Defense Ministry.
Tsvangirai said he faced a range of emotions at Monday's signing ceremony.
"People have traveled this long road," he said. "In this conflict of emotions, should we celebrate or restrain ourselves because of the uncertainty of the future?"
Tsvangirai decided to focus on the future, adding that he was "really moved by the mood of the people and the hope that is in the people."
