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HARARE, Zimbabwe (AP) — Zimbabwe's leaders launched a program on Wednesday to rewrite the nation's constitution ahead of an election planned next year.

The long-delayed program to amend a constitution adopted after independence from British colonial rule in 1980 already is nine months behind schedule under an agreement forming a 16-month-old coalition government between President Robert Mugabe and former opposition leader Prime Minister Morgan Tsvangirai after the disputed 2008 election.

Wednesday's launch ceremony started several hours late and scores of participants, including reporters, were barred entry at the main Harare convention center by police who said they did not have official invitations or entry passes.

Addressing the gathering, Mugabe and Tsvangirai called for open dialogue on a 60-day "outreach" program to canvass Zimbabweans for their views on a new constitution that would limit presidents to two five-year terms.

Mugabe, 86, who has been in power in Zimbabwe since 1980, opposes that plan.

The coalition agreement calls for a new constitution ahead of a foreign-monitored election planned in 2011.

The program to write a new constitution has been plagued by delays, bickering between coalition partners and shortages of cash to deploy lawmakers and officials to some 2,860 meeting centers across the country over the next two months.

Douglas Mwonzora, one of the organizers from Tsvangirai's Movement for Democratic Change party, said donors pledged $7 million for the program.

But human rights groups and the independent Zimbabwe Election Support Network reported accusations of intimidation by Mugabe party militants to muzzle contributions by ordinary people to the constitutional debate.

The election support network said in a statement that its monitors in rural areas noted "many villagers have been warned against speaking in the outreach process. Some individuals have been nominated and told what to say. This pattern has been observed in areas which experienced violence in 2008."

The organization said it urged Zimbabweans "to be strong and express themselves in this very critical process."

It said the nation's police commanders, blamed for bias toward Mugabe's party in years of political and economic turmoil, publicly declared they lacked cash and logistics to guarantee security during the constitutional program.

Long delays so far and lack of clear publicity also endangered the program aiming to finalize a new constitution by April 2011, followed by a new election.

"A hurriedly made constitution does Zimbabweans a disservice as this is the most important document in the governance of their country," the organization said.

The U.N. Food and Agriculture Organization, meanwhile, forecast worsening food shortages in coming months. In its latest bulletin, it said a resurgence of political violence was disrupting production and distribution of food in Zimbabwe.

The unstable political environment forced more Zimbabweans to flee the country, with more than 3 million already living in neighboring South Africa, it said.

Zimbabweans in self-exile, mainly economic fugitives, have asked to be included in the constitutional reform, but the outreach program organizers acknowledge they have failed to set up a promised web site in time.

Prime Minister Tsvangirai said Wednesday a new, democratic, people-driven constitution would be the nation's lasting legacy and his countrymen should resist intimidation in crafting it.

"All political parties have an obligation to ensure peace and cohesion," he said.

Mugabe said his views on constitutional changes differed with those of others.

"I want people to say their own views. We have agreed there should be no violence," he said, sitting alongside Tsvangirai.