BAGHDAD (AP) -- Concern over upcoming elections and widening tensions among Iraq's religious and ethnic groups appear behind the U.S. military's recommendation to put the brakes on withdrawing more American troops from Iraq despite improvements in security.

President Bush's top defense advisers have urged that he keep 15 combat brigades in Iraq until the end of the year - despite expectations that better security would allow for faster cuts, The Associated Press has learned.

The White House said Friday that Bush will announce his decision on future troops levels in Iraq next week.

The recommendation seems at odds with recent glowing reports from many fronts: al-Qaida in Iraq is on the run, the main Shiite militia has been pushed out of its strongholds in Baghdad, and Iraqi security forces have been handed control of Basra and Amarah and the former killing fields of Anbar province.

Meanwhile, U.S. military deaths are down to some of their lowest monthly levels since the war began in March 2003.

But U.S. military officials have been frank in saying that security gains - though impressive - are fragile. Political progress among Iraqi parties has lagged behind security improvements.

The Iraqi parties' commitment to achieving political agreements to ensure lasting peace will be severely tested in the coming months - and the U.S. clearly wants enough resources inside the country in case they fail.

The major challenge will likely come late this year when Iraqis elect ruling councils in the nation's 18 provinces. Those councils will wield considerable power over local security forces and resources, including oil.

American officials have long pressed the Iraqis to hold provincial elections to redress power imbalances created when many Sunnis and some Shiites boycotted the last local balloting in January 2005.

The boycott enabled the Kurds and Shiite religious parties to win a disproportionate share of power. A new election would give Sunnis a greater stake in the political process.

But the Kurds blocked the bill providing for those elections because they opposed a power-sharing plan for Kirkuk, the northern oil-rich area that the Kurds want to incorporate in their self-ruled region. Arabs and Turkomen want the Kirkuk area to remain under central government control.

Armed Kurdish forces militias have been moving into some northern towns outside their region, ostensibly to protect Kurdish populations there. But their presence adds pressure on the government to meet Kurdish demands for Kirkuk.

Parliament will try to approve a new election bill when it convenes next week after the summer recess. Vice President Adil Abdul-Mahdi said in a television interview Thursday that the government will go ahead with the balloting at the end of the year even if the measure stalls in parliament.

The election will intensify a series of ongoing power struggles involving not only the Kurds and Iraqi Arabs but also rival parties within the Sunni Arab and Shiite communities themselves.

In the Shiite south, mainstream Shiite parties that control the southern provinces now fear they will lose power to fellow Shiites loyal to anti-American cleric Muqtada al-Sadr.

Those fears were partly behind the government's decision last spring to crack down on al-Sadr's Mahdi Army militia in Baghdad and southern Iraq. Although the crackdown severely weakened the militias, al-Sadr retains a strong political following among disadvantaged Shiites who feel the mainstream Shiite parties have failed to improve their lives.

In the Sunni areas, the complication is over grass-roots movements that turned against al-Qaida and helped pacify Anbar and other areas. They now believe they deserve a share of the political power now held by the Iraqi Islamic Party, the mainstream Sunni political group within Prime Minister Nouri al-Maliki's government.

Some tribal sheiks in Anbar had urged the U.S. to delay handing over the province to Iraqi control until after the provincial elections. But the transfer went ahead last Monday.

At the same time, the Shiite-led central government is trying to rein in those Sunni movements, known as "Awakening Councils" or "Sons of Iraq." Such groups drew many of their members from the ranks of insurgents and supporters of Saddam Hussein.

Government forces have been arresting some Awakening Council leaders, and politicians close to al-Maliki have openly called for disbanding those groups, fearing they may switch sides again and turn their guns on the Shiites.

Washington has been paying the salaries of the nearly 100,000 Awakening Council members. But plans call for the government to assume the payments in Baghdad next month and nationwide by the end of the year.

Only about 15 percent of the Sunni volunteers have been given jobs in the army or police.

U.S. officials are clearly worried about the security risks if the government decides to cancel the pay of thousands of armed Sunni fighters without offering them jobs.