Iraq's constitution says the balloting must happen in January, and a delay will deepen uncertainty in a nation struggling to recover from years of war. Few predict a return to the intense violence that shattered Iraq, but profound mistrust among factions has made it hard for its democratic institutions to flourish.
"It is impossible to hold the elections in January from the legal and logistical point of view," said Qassim al-Aboudi, a senior official on the Independent High Electoral Commission. "We are going to wait for the result of the dispute before setting another date."
Vice President Tariq al-Hashemi, a Sunni Arab, had vetoed the law because he wanted more seats for Iraqis abroad, most of whom are Sunnis who fled sectarian bloodshed after the 2003 fall of Saddam Hussein. Iraq's parliament amended the law Monday with the backing of Shiite and Kurdish legislators, but lawmakers from the Sunni Arab minority skipped the vote, saying the Kurds stood to gain seats at their expense.
"What happened represents a dangerous precedent that will negatively effect the whole political process," al-Hashemi's office said in a statement. "And those who were behind this unfair and unconstitutional amendment will be held responsible for the consequences."
It said al-Hashemi "will deal with the new law as he did with the previous one to protect the national interest and bolster democracy."
Al-Hashemi's spokesman, Abdul-Ilah Khazim, said the vice president was likely to veto the law but declined to confirm that he would. Al-Hashemi and the two other members of the presidential council have 10 days to use their individual veto power.
President Jalal Talabani, a Kurd, said in a statement that the election guidelines met the aspirations of all Iraqis, "regardless of their religion, sect or ethnicity," and he appealed to al-Hashemi to accept the amended law.
The parliament can override a second veto with a three-fifths majority of all 275 lawmakers. Iraq's Shiites and Kurds make up about 80 percent of the country's population and have enough lawmakers in the legislature to override the veto and adopt the law.
The dealmaking that led to the amended law largely addressed complaints about the electoral system from the powerful Kurdish bloc, guaranteeing their support for the law. Lawmakers changed the basis for distributing seats, most likely giving more seats to the Kurds.
The number of seats in parliament will be expanded to about 320 to reflect population growth.
The United States has tied the pace of withdrawal of combat troops to the January date, though the U.S. military says that schedule is on track for now.
Under a deal with Iraq, all American forces must be out of Iraq by the end of 2011. President Obama has said he will pull out combat troops by August, and any delay could affect a possible military buildup in Afghanistan.
"It is very important for Iraq's future that these elections take place soon," U.S. Ambassador Christopher Hill told reporters. Hill, who has consulted with Iraqi lawmakers in recent days, said the amended law reflected efforts to meet the concerns of the vice president.
"I think this version does try to address the question of out-of-country voters, which was an issue very much on Mr. al-Hashemi's mind," he said. "So I would just ask people to study this very carefully and to understand that any law does involve some tradeoffs."
The amendment reshuffles the distribution of seats among Iraq's provinces, basing it on 2005 Trade Ministry statistics plus a 2.8 percent annual population growth, instead of the 2009 Trade Ministry figures.
The Kurds, who would likely benefit from the amended law, had threatened to boycott the elections if the three provinces they control in northern Iraq are not allocated more seats.
The amendment also says Iraqis living abroad will have their votes counted toward their home province, rather than allocating seats for voters outside Iraq, as al-Hashemi had requested.
On Tuesday, about 500 Sunni Arabs gathered in the northern city of Mosul, where insurgents retain a foothold, to denounce the amended law because they said it reduced the number of seats in their province, Nineveh.
Some were angry at al-Hashemi, saying his veto had backfired because it forced Shiites to make a deal with Kurds against the Sunni Arabs.
Sunni Arabs are unlikely to sit out the 2010 elections, a tactic that would deprive them of political clout. They boycotted Iraq's first post-Saddam parliamentary election in January 2005 in a move that left them without much influence in a legislature that drafted the country's constitution.
They took part in the Dec. 2005 election that produced the present parliament.
Also Tuesday, a Sunni Arab cleric died when a bomb planted in his car exploded in Saqlawiyah, west of Baghdad, said police Col. Adil Hussein and Saeed Mohammed, a tribal leader in the town.
The cleric, Ahmed Abdullah, had close links to the Iraqi Islamic party, a Sunni party that has cooperated with the Americans and the Shiite-led government, and whose members have been targeted by al-Qaida in Iraq.
Associated Press writers Sameer N. Yacoub, Sinan Salaheddin and Ryan Lucas contributed to this report.