Some Shi'ite religious parties in Iraq are refusing to accept defeat in last weekend's elections.

Candidates backed by radical cleric Moqtada al-Sadr say Saturday they will challenge the results because of alleged voting irregularities.

The initial tally, announced this week, indicated a solid election victory for the coalition of Iraqi Prime Minister Nouri al-Maliki, who has pursued a more secular agenda.

Mr. Maliki's State of Law coalition defeated Shi'ite religious parties in the capital, Baghdad, and Iraq's second largest city, Basra. The prime minister's allies also took the lead in at least eight other Shi'ite-dominated provinces.

The vote is seen as a referendum on Mr. Maliki's leadership ahead of national parliamentary elections later this year.

Meanwhile, senior U.S. defense officials say the White House is considering three different timelines, ranging from 16 to 18 months, for withdrawing U.S. troops from Iraq.

The officials, none of whom have been identified, told several Western news agencies that the Pentagon has submitted assessments of the risks associated with three options for troop withdrawal, in response to a White House request.

A 16-month pullout would be in line with a pledge that President Barack Obama made during his campaign.  

The risk assessments were first reported by the U.S.-based McClatchy Newspapers, and later confirmed by other news agencies - the Associated Press and the French news agency, AFP.

McClatchy quotes a senior administration official as saying Mr. Obama is likely to announce his strategy for Iraq by mid-March.

The White House said several days ago that Mr. Obama has spoken to the Iraqi prime minister about the planning process for withdrawing U.S. troops from Iraq.  

The status-of-forces agreement the United States signed with Iraq late last year says U.S. troops must be out of the country by the end of 2011.

Some information for this report was provided by AFP and AP.