BAGHDAD — Major Shiite groups have formed a new alliance that will exclude the Iraqi prime minister, lawmakers said today, a move likely to stoke fears of increasing Iranian influence and shake up the political landscape ahead of January parliamentary elections.

The coalition will include the largest Shiite party, the Iranian-backed Supreme Iraqi Islamic Council and anti-U.S. cleric Muqtada al-Sadr's bloc, which could give Tehran deeper influence in Iraq just as U.S. forces begin to withdraw.

The last American soldier is scheduled to leave Iraq by the end of 2011.

Prime Minister Nouri al-Maliki's Dawa Party was left out because of disagreement over who would lead the alliance, senior SIIC member Reda Jawad Taqi told The Associated Press. He said a last-minute meeting held Sunday in a bid to bring Dawa into the coalition had failed to overcome the differences.

Key figures in the alliance said efforts continued to try to reach agreement with Dawa.

"We are hoping for their participation and the door will be left open for them," ex-Prime Minister Ibrahim al-Jaafari said.

The announcement was a new setback for al-Maliki, whose efforts to portray himself as a champion of security has been battered by a series of devastating bombings in Baghdad and in northern Iraq in recent weeks. The most recent of these struck the foreign and finance ministries on Wednesday, killing about 100 people and wounding 500.

The uptick in violence has heightened fears that Iraqi security forces aren't ready to protect the people nearly two months after most U.S. troops pulled back from urban areas.

Iraqi Vice President Adel Abdul-Mahd also reached out to Dawa, saying it was important to present a strong united front.