The Iranian-backed Shiite parties that helped propel Iraq's prime minister into power three years ago dumped him Monday as their candidate for re-election, forming a new alliance to contest the January vote. The move dealt a blow to Nouri al-Maliki's chances to keep his job next year and set the stage for a showdown between competing factions in the Shiite coalition that had dominated Iraq's government since the fall of Saddam Hussein in 2003. Al-Maliki now faces pressure to make a deal with minority Sunni parties to strengthen his position. Because his Dawa party is relatively small, he has never been able to rely on a loyal political base. Instead, he has developed a reputation as a strong leader by crushing militias loyal to anti-American Shiite cleric Muqtada al-Sadr in Baghdad and in the southern city of Basra. The Shiite prime minister's efforts to win public confidence by portraying himself as a champion of security have taken a battering in recent weeks. A wave of horrific bombings has called into question the government's ability to protect the Iraqi people two months after most US forces pulled out of urban areas. In the latest violence, bombs attached to two buses en route from Baghdad exploded less than an hour apart near the mainly Shiite city of Kut on Monday, killing at least 11 people and wounding 20, police and hospital officials said. Local police chief Brig. Gen. Raed Shakir Jawdat said the explosives were detonated with timers. Monday's political announcement - made with fanfare at a news conference - represents a major realignment. The new bloc, called the Iraqi National Alliance, will include the largest Shiite party, the Supreme Iraqi Islamic Council, or SIIC, and al-Sadr's bloc, which both have close ties to Teheran. Although some small Sunni and secular parties are joining the alliance, many Sunnis consider the Supreme Council as little more than an instrument of Shiite Iran. If the alliance does well in the Jan. 16 vote, Teheran could gain deeper influence in Iraq as US forces pull back, with a full American withdrawal planned by the end of 2011. Al-Maliki's Dawa Party also has close ties to Iran, but the prime minister has tried in recent years to persuade Teheran to stop interfering in Iraq. Iran is accused of supporting Shiite militias, despite its denials of the allegations. Al-Maliki, who took office in May 2006 with the blessing of the Supreme Council and the Sadrists, has become increasingly assertive as his popularity has grown with the sharp decline in violence. He has taken on the Americans, the Iranians, the Sunnis and fellow Shiites alike. His loyalists ousted the Supreme Council from control of the oil-rich southern Shiite heartland in provincial elections earlier this year, raising concern among other Shiite politicians that internal divisions could cost them seats to Sunnis in the upcoming parliamentary elections. But the unrelenting explosions - including two suicide truck bombings against the foreign and finance ministries that killed scores last week - have weakened his position at a crucial time. He stayed out of the new alliance because leaders refused to guarantee him the prime minister's spot, officials said. Rumored possibilities for the job include new alliance members ex-Prime Minister Ibrahim al-Jaafari, current Vice President Adel Abdul-Mahdi and even Former Deputy Prime Minister Ahmad Chalabi, a one-time Pentagon favorite. The realignment does not immediately threaten al-Maliki's position as prime minister, but points to stormy politics in the election campaign and beyond, as US troops begin scaling back their presence. Supreme Council lawmaker Reda Jawad Taqi said a last-ditch meeting was held Sunday to try to bring al-Maliki into the fold but it failed to overcome the differences. One of al-Maliki's advisers, Hassan al-Sineid, said in a televised response that the prime minister and the leaders of the new alliance differed over "the mechanism of participation in the alliance and the need to open this alliance to include a broad range of political powers." The prime minister instead is working to form an alternate coalition. He is reaching out to a prominent Sunni sheik in Anbar province, whose followers include fighters who joined forces with the Americans against al-Qaida in Iraq. Sheik Ahmed Abu Risha said his representatives met with al-Maliki's advisers on Sunday to discuss forming "a national and nonsectarian alliance." He praised al-Maliki for cracking down on Shiite militias and supporting the anti-al-Qaida movement that has spread nationwide and is considered a key factor in a sharp decline in overall violence over the past two years. Despite Monday's announcement, the new Shiite alliance was careful to leave the door open for the Dawa Party to join later. Abdul-Mahdi, a top SIIC member, was among those reaching out to Dawa, saying it was important to present a strong united front that can address the overwhelming challenges facing the country. The coalition will replace the United Iraqi Alliance, which won control of parliament in the last parliamentary elections in December 2005 but began to unravel later with the withdrawal of two major factions and the bitter rivalry between al-Maliki and the Supreme Council. The list includes several Sunnis, comprising a smaller Awakening Council faction from the western Anbar province that won several seats in provincial elections earlier this year. Absent from the press conference was the Supreme Council's leader Abdul-Aziz al-Hakim, who suffers from lung cancer and was hospitalized this weekend in Iran after officials said his health deteriorated. Al-Sadr also is believed to be in Iran.