UPDATE 3-Guinea election leader secures backing for run-off
* 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. Continued...