BAGHDAD, Iraq — Iraq's ruling Shiites have voiced growing concern that the United States is subtly shifting support to Sunni Arabs, the bulwark of Saddam Hussein's dictatorship, in a bid to salvage 43 months of democracy-building in Iraq and tamp down violence.

The perceived newly energized bid to draw the Sunni insurgency into Iraq's political process marks, in the eyes of anxious Shiites, a worrisome and major alteration of American policy in a period that has seen growing strains in the U.S.-Iraqi relationship.

Shiites in Iraq were not alone in sensing the change.

"There is much talk of such a shift, and it is in part driven by the (American) desire to contain Iran," said Vali Nasr, an expert on Shiites who lectures at the U.S. Naval Postgraduate School in Monterey, Calif.

"There is also frustration with the inability of Shiites to govern," he said.

The United States had relied heavily on the majority Shiite sect in its effort to construct a constitutional democracy to replace Saddam's Baath Party dictatorship.

U.S. dependence on the Shiites grew exponentially, starting in late summer of 2003, when disaffected Sunnis, aided by foreign fighters and al-Qaida terrorists, launched the insurgency. The insurgency is largely responsible for the climbing U.S. death toll and setting in motion the current chaos and sectarian violence gripping Baghdad and much of central Iraq.

Shiite anxiety deepened after U.S. Ambassador in Iraq Zalmay Khalilzad said last month that Prime Minister Nouri al-Maliki's Shiite-dominated government was on board with a set of timelines for progress.

Al-Maliki said he was not consulted about the plan, which included a call for deadlines to disband Shiite militias and ensure equitable sharing of Iraq's oil wealth among all religious and ethnic groups. The plan also called for remodeling a commission that is charged with excluding Baath Party members from important jobs into a body to reconcile religious and ethnic differences.

Sensing Washington's about-face, al-Maliki responded to Khalilzad's proposals with a public rejection of the timeline and a series of unusually strong comments asserting his government's independence.

Analysts like Nasr and Iraqi politicians said Washington's perceived shift away from total support for the Shiites also was in part dictated by its desire to find an exit strategy from Iraq through a new power-sharing formula.