KABUL: Former foreign minister Abdullah Abdullah received a boost in the race for Afghan presidency on Sunday when one of the pre-election favourites dropped out and backed his team ahead of next month’s expected run-off.

Zalmay Rassoul, who finished third in April’s first round with 11.5 per cent of the vote, told journalists in Kabul he had endorsed Abdullah to strengthen national unity, and because the pair campaigned on similar platforms.

Preliminary results showed Abdullah and his closest rival, former World Bank economist Ashraf Ghani, sharing over 75 per cent of the vote but neither winning an absolute majority.

The Afghan election commission will announce official results of the first round of voting on Wednesday, in which President Hamid Karzai was constitutionally barred from running.

Evidence of widespread fraud reported by the country’s Independent Election Complaints Commission have taken the gloss off the third presidential poll since US-led forces drove the Taliban from power in 2001.

The vote marks the first democratic transfer of power in the country’s history, however, uncertainty over the outcome risks stalling crucial foreign aid and economic reform.

Analysts said delays could also foment ethnic tensions and leave a political vacuum in which the Taliban could take advantage.

Rassoul, another ex-foreign minister, was considered one of the pre-election favourites, having won the backing of some members of the powerful Karzai family.

Rassoul’s backing for Abdullah was seen as crucial, given most of his support is from the Pashtun-dominated south of the country. Abdullah, who is half-Pashtun and half-Tajik, draws most of his support from the Tajik community in the north.