KAMPALA (Reuters) - Uganda's opposition said on Wednesday they had formed a coalition to back one presidential candidate in next year's election, a move analysts say will pose a stronger challenge to the ruling party but not enough to unseat the president.
President Yoweri Museveni, 70, who has been in office for close to three decades, is widely expected to run again as the candidate for his National Resistance Movement (NRM) party.
Museveni is unencumbered by term limits facing some other African leaders. Uganda scrapped a two-term limit in 2005 when the constitution was changed to allow for multi-party politics.
But some Western donors have criticized Museveni for hanging on to office and opponents have accused the government of harassing them and rigging past votes, a charge officials deny.
Aid-reliant Uganda, which has also won Western praise for sending troops to battle Islamist militants in Somalia, is expected to hold parliamentary and presidential elections between February and March next year.
The Forum for Democratic Change, Uganda's biggest opposition party, and others said in a statement read out at a news conference that they would form The Democratic Alliance.
"We have also agreed through this alliance that we'll field a joint presidential candidate," according to the statement, which was backed by Uganda People's Congress, the Democratic Party, the Conservative Party, Jeema party and others.
Opposition parties have united before but past coalitions have been smaller and fragile, often swiftly collapsing at the slightest spat. They have struggled to mount a significant challenge to Museveni, still credited by many for restoring order after years of chaos under autocrats like Idi Amin.
"Museveni is an expert at defeating a united opposition," presidential spokesman Tamale Mirundi said. "These people will disagree down the road ... It's only a matter of time."
Opposition leaders attended Wednesday's news conference, which analysts said was a sign of resolve because it meant they were personally stamping their seal of approval on the plan.
A committee will manage the process to select a candidate, but the parties did not give more details.
The Forum for Democratic Change, led by Mugisha Muntu who fought alongside former rebel leader Museveni in the bush, has threatened to block the vote if the government rejects demands for an independent electoral commission and new voters' list.
The president appoints the commission's top officials.
Opponents say the government has in the past used its supporters to infiltrate opposition groups to stoke dissent.
"Museveni will start working to create cracks ... in the alliance," said newspaper commentator Nicholas Ssengoba. "Soon we'll be hearing disagreements and one opposition leader attacking the other."
(Editing by Edmund Blair and Andrew Heavens)