Sadr's organisation on Wednesday said it decided to ally itself with the Sunnis due to "the difficult situation facing the country, to prevent the occupier and enemies of Iraq from attaining their goals, to consolidate national identity and to reaffirm its unity".
Sadr and his followers vehemently oppose the US-led occupation of Iraq, and have aligned with Sunni Arabs who are believed to form the backbone of the persistent anti-US street war in Iraq.
Al-Anbar is the most volatile province in Iraq and includes the Iraqi fighters' strongholds of Ramadi and Fallujah, which overwhelmingly rejected the Iraqi constitution that was approved by referendum on 15 October.
Sadr's office, in a statement released in the Shia holy city of Najaf south of Baghdad, said: "The deputy Fattah al-Sheikh has been designated to form a list in al-Anbar for the elections."
Shaikh told AFP he would "run in al-Anbar at the head of a list that includes eight Sunni candidates.
Sadr and his followers oppose
the US-led presence in Iraq
"Consultations have taken place in recent days to create a national Islamic force" to run against a secular bloc being mooted by former prime minister Iyad Allawi, he said.
The talks are continuing, he added.
Three Iraqi Sunni parties announced on Wednesday they are forming a coalition to run in the next elections on 15 December.
Meanwhile, Kuwait and Saudi Arabia called for unity in neighbouring Iraq on Wednesday after the adoption of a new constitution despite opposition from the Sunni Arab elite.
"We can't say yes or no to the constitution because this is a
matter for the Iraqi people and it is in our interest not to
interfere," Saudi Crown Prince Sultan bin Abdul Aziz was quoted as saying.
"But we do hope the Iraqi people will unite in an independent
Arab country," he added, according to the official SPA news agency.
The charter was approved by 78% of Iraqi voters in a
referendum but was overwhelmingly opposed in two Sunni-majority governorates and more narrowly rejected in a third.
Saudi Arabia has been treading a fine line in its relations with
its northern neighbour, where the Shia now lead the
government for the first time in Iraq's modern history.
The Saudi kingdom is predominantly Sunni who adhere to a strict interpretation of Islam and regard the Shia as an aberration.
Foreign Minister Saud al-Faisal recently warned of meddling by
Saud al-Faisal (R) warned Iran
against meddling in Iraq
Shia-ruled Iran in Iraqi affairs prompting a sharp response from Iraqi Interior Minister Bayan Baqer Sulagh who is himself a Shia and follower of Iraq-based Iranian Shia cleric Ali Sistani.
Sulagh eventually apologised.
Kuwaiti leaders also voiced hope the constitution would help
"We express our sincere wishes for Iraq and its people to
achieve progress and prosperity and lay strong foundations for
democracy and equality," Emir Sheikh Jaber al-Ahmad al-Sabah said.
Prime Minister Sheikh Sabah al-Ahmad al-Sabah said he hoped for "more understanding, solidarity and unity" among the Iraqi people.
Kuwait was invaded by Saddam's forces in 1990, but was liberated seven months later by a US-led international coalition.
The oil-rich emirate, a staunch US ally, served as the launch pad for the US-led invasion that toppled he government of Saddam Hussein in April 2003.