US President Barack Obama on Tuesday welcomed President Hamid Karzai's agreement to hold a second round of voting in Afghanistan's disputed election as an important precedent for Afghan democracy.
"I welcome President Karzai's statement today accepting the Independent Electoral Commission's certification of the August 20 election results, and agreeing to participate in a second round of the election," Obama said.
"This is an important step forward in ensuring a credible process for the Afghan people which results in a government that reflects their will," Obama said in a written statement.
The United States and its allies had been imposing intense pressure on Karzai to agree to a second election, or to frame a national unity government, after massive fraud tainted the first round of voting.
Senior US officials warned at the weekend that Obama would be unable to conclude a policy review and decide whether to send up to 40,000 more US troops into the Afghan war without a legitimate governing partner in Kabul.
In his statement, Obama congratulated Afghans for showing "patience and resilience" through the drawn-out election progress, saying it was extraordinary after years of war that they were able to hold an election at all.
He also lauded the Independent Electoral Commission and the Electoral Complaints Commission for carrying out their mandates, a procedure that led to the November 7 run-off vote.
"Throughout this process, the United States has been interested above all in the strength and independence of those institutions, and the need for them to fulfill their mandate on behalf of all Afghans."
Obama also offered congratulations to Karzai and his top rival, ex-foreign minister Abdullah Abdullah, for winning countrywide support.
"It is now vital that all elements of Afghan society continue to come together to advance democracy, peace and justice.
"We look forward to a second round of voting, and the completion of the process to choose the President of Afghanistan.
"In that effort, the United States and the international community are committed to partnering with the Afghan people."
Exactly two months on from polls that Karzai had been expected to win easily, the Independent Election Commission (IEC) confirmed Tuesday that he had fallen short of the 50 percent needed to avoid a run-off against Abdullah.
Karzai confirmed at a news conference in Kabul that he would take part in the second round, calling it a "step forward for democracy".
He spoke alongside UN envoy Kai Eide and US Senator John Kerry, whose presence in Kabul underscored intensive Western lobbying of Karzai to resolve the weeks of political paralysis.
Karzai also urged the international community to help ensure the second round can pass off peacefully, with about 100,000 US-led troops fighting a worsening Taliban insurgency.
On Monday, a UN-backed watchdog confirmed staggering levels of fraud in the August 20 vote, declaring more than one million ballots suspect -- a quarter of the total cast.
An election official confirmed that from a preliminary tally of 55 percent, Karzai's share of the first-round vote had now fallen to 49.67 percent.
Karzai had initially dismissed allegations of widespread fraud as fabricated, convinced he had won a clear victory, but international pressure has been mounting in recent weeks.