Iraqi Prime Minister Nouri Maliki has vowed to contest the results of parliamentary elections that saw former PM Iyad Allawi win by only two seats.
Speaking on national TV, Mr Maliki said he would challenge the count through what he described as a "legal process".
Mr Allawi's secular Iraqiya bloc won 91 of parliament's 325 seats. Mr Maliki's State of Law won 89 seats, followed by the Iraqi National Alliance on 70.
Earlier, UN envoy to Iraq Ad Melkert said the election had been credible.
He also called on all parties to accept the outcome.
The sentiment was echoed by US Ambassador Christopher Hill and the top US commander in Iraq, Gen Ray Odierno, who said they supported the conclusions of election observers that there had been no evidence of widespread or serious fraud during the 7 March poll.
A credible election was seen as crucial in helping to stabilise Iraq before the planned withdrawal of US combat troops by the end of August.
Sectarian violence erupted as politicians took months to form a government after the last parliamentary election in 2005.
On Friday, at least 42 people were killed in twin bombings near a restaurant in the town of Khalis, 80km (50 miles) north of Baghdad.
Following the announcement of the final results by Iraq's Independent High Electoral Commission (IHEC), Mr Allawi promised to "work with all sides, whether they won or did not win in the election, to form the next government".
"Iraqiya will open its heart to all political forces and all those who want to build Iraq, and we will together bury political sectarianism."
Mr Allawi, a Shia, fought on a secular platform and many who voted for him were Sunnis. His bloc includes Sunni Vice-President Tariq al-Hashemi.
His victory means he will be given the first opportunity to form a coalition government with a majority of 163 seats. If he fails to do so within 30 days, Iraq's president will ask the leader of another bloc.
Prime Minister Maliki, however, refused to accept the results, telling a news conference in Baghdad that they remained only "preliminary".
He has until Monday to register his complaints with electoral officials.
"When we checked some of the [election] papers we found a large percentage were forged," he said.
"Another thing, witnesses from the IHEC talked about manipulation in the election and underlined this with names and other cases, which made it clear that there was a defect, which should be dealt with through manual counting."
Mr Maliki is reportedly also negotiating a merger with the Iraqi National Alliance, which includes followers of the radical Shia cleric Moqtada al-Sadr, so he can claim to lead the biggest bloc in parliament. The groups had been part of the governing United Iraqi Alliance (UIA) before the election, but split acrimoniously.
Election officials have refused calls for a recount, and international observers have described the election as fair and credible.
"From our vantage point and from the international community's vantage point, we have not seen any evidence of substantial fraud that would fundamentally change the outcome," said US State Department spokesman PJ Crowley.
"This marks a significant milestone in the ongoing democratic development of Iraq," he added.
- Al-Iraqiyya (Iraqi National Movement): Nationalist bloc led by former PM Iyad Allawi, a secular Shia. Includes Vice-President Tariq al-Hashemi, a Sunni Arab, and senior Sunni politician Saleh al-Mutlaq
- State of Law: Led by Prime Minister Nouri Maliki and his Shia Islamist Daawa Party, the alliance purportedly cuts across religious and tribal lines. Includes some Sunni tribal leaders, Shia Kurds, Christians and independents
- Iraqi National Alliance (INA): Shia-led bloc includes followers of the radical cleric, Muqtada al-Sadr, the Supreme Iraqi Islamic Council (SIIC), and the Fadhilah Party, along with ex-PM Ibrahim Jaafari and Ahmad Chalabi
- Kurdistan Alliance: Coalition dominated by the two parties administering Iraq's semi-autonomous Kurdish region - the Kurdistan Democratic Party (KDP) and Patriotic Union of Kurdistan (PUK), led by President Jalal Talabani