KABUL: Afghanistan's two presidential candidates have signed a power-sharing deal for the roles of president and chief executive three months after a disputed runoff that threatened to plunge the country into turmoil and complicate the withdrawal of US and other foreign troops.

Ashraf Ghani Ahmadzai, who will become president, and Abdullah Abdullah signed the national unity government deal as outgoing President Hamid Karzai watched.

The deal follows weeks of negotiations on a power-sharing arrangement following accusations of fraud in the June runoff vote.

The deal is a victory for US Secretary of State John Kerry, who first got the candidates to agree in principle to share power during a July visit.

The inauguration to replace Karzai — who has been in power since late 2001 — is expected within days.

The final vote count is also scheduled for release, after being delayed for last-minute talks to break a deadlock that has plunged Afghanistan into crisis as US-led troops end their 13-year war against the Taliban.

Ashraf Ghani — who won June's run-off vote according to preliminary results — is set to emerge as president, with Abdullah Abdullah nominating his pick for the new post of “chief executive officer”, possibly taking on the role himself.

Both Ghani and Abdullah claim to have won the fraud-tainted election, and the United Nations has pushed hard for a “national unity government” to avoid a return to the ethnic divisions of the 1990s civil war.

“Both candidates are expected to sign an agreement on the structure of National Unity [Government] tomorrow,” Aimal Faizi, spokesman for outgoing President Hamid Karzai, said on his Twitter account late Saturday.

Under the Afghan constitution, the president wields almost total control, and the new government structure will face a major test as the country's security and economic outlook worsens.

The vote count has been plagued by months of setbacks amid allegations of massive fraud, emboldening the Taliban insurgents and further weakening the aid-dependent economy.

“The IEC will officially announce the final result of the presidential election tomorrow,” Independent Election Commission spokesman Noor Mohammad Noor told AFP on Saturday.

The future of Afghanistan's relationship with the US-led Nato alliance also hangs in the balance after Karzai refused to sign a security agreement to ensure a continued foreign military presence after this year.

Nato's top military commander said a unity government would enable the rapid conclusion of the agreement.

“We are hoping for very fast signatures. And that would be important because it brings great stability to the conversation of our continued support,” US General Philip Breedlove said on Saturday.

“We've had fruitful conversations with both of the candidates. We believe that they are very, very close also to forming that unity government, which we think is very important,” he said.

Uneasy alliance?

A ruling coalition between the opposing camps is likely to be uneasy after a bitter election that has revived some of the ethnic loyalties of the civil war that led to the Taliban taking power in Kabul in the 1990s.

Abdullah, a former anti-Taliban resistance fighter, draws his support from Tajiks and other northern ethnic groups. Ghani, an ex-World Bank economist, is backed by Pashtun tribes of the south and east.

But Ghani's spokesman said the power-sharing pact had been secured and that details would be released at a signing ceremony on Sunday, without giving a time.

After the June run-off election was engulfed in fraud allegations, the United States brokered a deal in which the two candidates agreed to abide by the outcome of an audit of all eight million ballot papers and then form a national unity government.

But Abdullah later abandoned the audit, saying it was failing to clean out fraud. He won April's first round, only to see Ghani come from well behind and win in June.

The new administration will have to stabilise the economy as international aid falls, and deal with worsening unrest nationwide.

Efforts to open a peace process with the Taliban failed under Karzai and may be revived.

A total of 2,312 civilians were killed in the first eight months of this year, an increase of 15 percent from 2013.

About 41,000 Nato troops remain in Afghanistan, down from a peak of 150,000 in 2010, fighting alongside Afghan soldiers and police against the fierce Taliban insurgency.

Nato's combat mission will end in December, with a follow-on force of about 12,000 troops likely to stay into 2015 on training and support duties.

Pakistan welcomes the agreement signed by the two Presidential candidates

Pakistan has welcomed the agreement signed by the two presidential candidates in Afghanistan regarding the establishment of a government of national unity.

"Consistent with our support for a peaceful democratic transition, we regard the signing of this agreement as a positive development and this outcome has been possible due to the wise and sagacious leadership of Dr. Ashraf Ghani and Dr. Abdullah Abdullah", a foreign office spokesperson said in a statement.

"We congratulate the two leaders and the brotherly people of Afghanistan and reaffirm Pakistan’s support for all their efforts to build a peaceful, stable and unified Afghanistan". The spokesperson remarked.