* First-placed candidate secures key backing with deal
* Toure party promised PM’s post if Diallo wins - source
* Guineans voted along ethic lines in first rounds
(Recasts with signing, adds quotes)
By Saliou Samb
CONAKRY, July 28 (Reuters) - The candidate who came top in the first round of Guinea’s presidential election, Cellou Dallein Diallo, became strong favourite on Wednesday to win the decisive run-off by securing the backing of a leading rival.
Diallo signed a deal with third-placed Sidya Toure, making him the likely next president following the elections, which are are meant to pave the way for a return to civilian rule in the world’s top exporter of the aluminium ore bauxite.
Toure became a possible king-maker after he secured 13.62 percent of the vote in the first round in June behind Diallo, who won 43.69 percent, and second-placed Alpha Conde.
No date has been set yet for the run-off between the top two candidates in Guinea, which has been gripped by political uncertainty since a coup in late 2008.
“I express my thanks to Mr Sidya Toure for having agreed to ally himself with us,” Diallo said after the pair signed the agreement in Conakry.
No details were made public but sources in Diallo’s UFDG party said Toure’s party had been promised the post of prime minister and 30 percent of cabinet jobs in return for its support, should Diallo win.
“(The choice) for the second round is difficult. But our priority is that Guinea should at last launch its economic development. That is why we made the choice (we made),” Toure told reporters journalists after the signing ceremony.
Toure told Reuters last week that he would negotiate with the two leading candidates to try to secure an alliance.
Sixth-placed Ibrahima Abe Sylla’s NGR and the PUP former ruling party also signed the agreement to support Diallo, a 58-year-old former minister and prime minister under the late President Lansana Conte.
Months before Guinea held its election, Rio Tinto and Vale surprised many by saying they would spend billions on iron ore projects there. Analysts expect some contracts will be reviewed after the elections but a Diallo victory could ease fears.
“We don’t believe that Conde will put together a comparable coalition and we expect Diallo to be the next president of Guinea, barring any unexpected reintervention from the army,” said Chris Melville, senior associate at Menas Associates.
“Diallo has spent recent months getting close to members of the transitional government and his victory would provide some reassurance to mining companies that have signed agreements with the (transitional government),” Melville told Reuters.
Results from the first round showed the importance of ethnic allegiance, with Diallo and Conde taking votes from their own large ethnic groups -- Peul and Malinke, respectively.
Toure’s Diakhante minority makes up just one percent of the population but if he can repeat his first round performance, and there is no significant anti-Peul mobilisation, Diallo looks set to win.
“I think that (Toure‘s) supporters will do what he tells them to do. I don’t think there will be a lot fading off,” a diplomat who follows Guinea told Reuters.
Conde has opposed all three recent and generally unpopular leaders -- Captain Moussa Dadis Camara, who seized power when Conte died but was replaced by an interim leader after being shot last year, Conte himself, and Sekou Toure.
European and U.S. observers broadly praised conduct of the June 27 first round vote following months of political tension and wrangling, which included the killing of dozens of pro-democracy demonstrators last year.
But the process revealed a number of logistical problems which experts say poll organisers need to fix before a potentially tense and close second round of voting. (Additional reporting and writing by David Lewis; editing by David Stamp)