A top aide to Iraq's Shiite spiritual leader on Friday urged the country's fractious political blocs to solve a crisis over a key election law that threatens to delay national polls planned for January.

Sheik Abdul-Mahdi al-Karbalaie, the representative of Grand Ayatollah Ali al-Sistani in the holy city of Karbala, told worshippers during his regular Friday sermon that failure to break the deadlock could lead to a "constitutional vacuum" that would create "great dangers for Iraq."

"I call upon all brothers in the political blocs to reach a reasonable solution so that elections can take place on time and avoid these consequences and dangers," al Karbalaie said.

Parliament is to vote Saturday on how to resolve the crisis triggered by Vice President Tariq al-Hashemi's veto of the legislation earlier this week. Al-Hashemi, a Sunni Arab, wants more seats allocated for Iraqis living abroad, many of whom are Sunni.

Lawmakers spent weeks wrangling over the long-delayed bill before finally passing it on Nov. 8, much to the relief of Iraqi leaders and the United States.

But the veto threw into question whether the vote can be held by the end of January, as mandated in Iraq's constitution.

While al-Sistani's words carry great weight with his fellow Shiites — most of whom support the election law — they hold no power over those who have objected to the election legislation — al-Hashemi and other Sunni Arab politicians, as well as Iraq's Kurds.

Earlier this week, Kurdish leaders threatened to boycott the elections unless the three provinces they control in northern Iraq are guaranteed more seats in the next parliament, which will expand from the current 275 seats to 323.

Lawmakers plan to vote on two options: sending the same election law back to the three-member presidency council, where it is likely to be vetoed again, or amending the law to address al-Hashemi's concerns. If the legislation is vetoed a second time, parliament can override it with a three-fifths majority.

Washington has tied the pace of a major troop drawdown to the elections. So far, U.S. military commanders say their timetable for withdrawing all combat troops by the end of August 2010 are still on track.