Washington: The White House welcomed Afghanistan’s presidential run-off election on Saturday as a “significant step” for the country’s democracy, but emphasised the need for electoral commissions to legitimise the vote.

“The work of the electoral commissions in the weeks ahead will be particularly important,” the White House said in a statement, commending “the voters, electoral bodies and security forces for their commitment to the democratic process”.

Millions of Afghans cast their votes despite Taliban threats to decide whether former foreign minister Abdullah Abdullah or ex-World Bank economist Ashraf Gani will lead the country into a new era of declining international military and civilian assistance.

“These elections are a significant step forward on Afghanistan’s democratic path, and the courage and resolve of the Afghan people to make their voices heard is a testament to the importance of these elections to securing Afghanistan’s future,” the White House said.

Secretary of State John Kerry praised Afghans who “defied the threat of violence and went to the ballot box” because of their dedication to a “more inclusive, prosperous and stable future”.

General Lloyd Austin, head of the regional US military command Centcom, commended Afghan security forces “for the outstanding job they did securing polling stations and providing for the safe transit of the Afghan people”.

“The strong performance of the ANSF (Afghan National Security Forces), under what were very challenging circumstances, is further testament to their growing capability,” Austin said, as Nato prepares to withdraw its troops later this year.

US Defence Secretary Chuck Hagel commended Afghan security forces in ensuring a safe round of voting, according to his spokesman Rear Admiral John Kirby.

The Pentagon chief “looks forward to working with the next Afghan administration as we bring our combat role to a conclusion, begin our new post-2014 assistance mission, and build a strong and enduring security relationship”, Kirby added.

The peaceful election “highlights the growing competence and capability of Afghan National Security Forces, who once again took the lead in making safe their fellow citizens’ access to the ballot box”, Kirby said.

Fraud allegations likely

Abdullah and Gani emerged as the leaders of an eight-man field in an April election, triggering the run-off as neither reached the 50 per cent threshold needed for outright victory.

However, fraud allegations are likely from both campaign teams, and a close count could lead to a contested result as the country undergoes its first democratic transfer of power.

Kerry urged the process be kept “transparent and accountable” and called on the candidates and stakeholders to “work with the electoral commissions and respect their conclusions”.

President Hamid Karzai, who has ruled Afghanistan since 2001 and was re-elected in a 2009 vote marred by ballot-box stuffing, is constitutionally barred from a third term in office.

Counting the ballot will take weeks. The preliminary result is due on July 2 and a final result on July 22.