BAGHDAD (Reuters) - Sitting in his small room in northern Baghdad, a pistol nearby and assault rifles stacked under the bed, Khalil Ibrahim is worried over Iraq’s future.

Iraqi policemen stand guard at a checkpoint in Baghdad June 28, 2009. REUTERS/Bassim Shati

Six years after the U.S. invasion, Iraqis are contemplating the reality of life after a major milestone -- Tuesday’s withdrawal of U.S. combat troops from urban centres.

Glancing at his seven-year-old son playing a war game on a computer in the corner, Ibrahim, a chain-smoking former military intelligence officer, said he has two main worries.

“Iran has good relations with our political parties. They run militias. If the U.S. troops complete their withdrawal, Iran will do whatever it wants in Iraq,” he said, scowling.

Shi’ite-ruled Iran is often accused of arming and funding Shi’ite militias who have killed Sunnis, a charge Tehran denies.

“Also, if the Americans pull out, al Qaeda will return,” Ibrahim said. He knows the Islamist militants better than most.

As leader of a U.S.-backed Sunni Arab guard unit made up of many former insurgents, some of his men fought with the rebels against the U.S. military, before switching sides and helping drive al Qaeda fighters out of much of Iraq.

But as U.S. forces increasingly hand control to Prime Minister Nuri al-Maliki’s Shi’ite Muslim-led government under a security pact that requires them to withdraw completely by 2012, tensions are rising.

Violence has dropped sharply across Iraq, but militants still launch devastating bombings. They are usually blamed on Sunni Arab insurgents like al Qaeda, and seem aimed at undermining Maliki’s administration and tipping the nation back into the sectarian slaughter of 2006/07.

WAVE OF BOMBINGS

The last few days have seen two of the worst attacks in more than a year. A suicide truck bomb killed at least 73 worshippers leaving a Shi’ite mosque near northern Kirkuk city on June 20. Four days later another blast tore through a market in Baghdad’s Sadr City, a Shi’ite slum, killing 72 people.

The government has warned that bloodshed is likely to intensify ahead of an even more important milestone for Iraq than this week’s -- a parliamentary election due in January.

With the U.S. withdrawal from cities, many Iraqis from Shi’ite and Sunni sects say they feel exposed to what they say is corruption and incompetence afflicting Iraqi security forces.

“We’re afraid of what will happen in the next few days,” 40-year-old Shi’ite civil servant Salah Abd told Reuters by the wreckage of the Sadr City blast. “We could lose a lot of lives.”

Others are more optimistic about the U.S. withdrawal, which will see almost all U.S. troops pull back to rural bases.

“The Iraqi forces will improve, and then they will be better than Americans because they have our best interests at heart,” said a 44-year-old Shi’ite woman called Marwa. She was taking advantage of the quiet weekend streets to shop for a digital camera in the upmarket Karrada district.

U.S. military officials say they have plans in place that will let them redeploy if Iraq asks for their help. And their main bases in violent northern provinces have all been defined as “rural” to allow them to retain a presence.

AL QAEDA IN IRAQ

At his apartment in northern Baghdad’s run-down Adhamiya neighbourhood, Ibrahim, who also goes by the name of Abu Omar, remained sceptical.

Al Qaeda frequently targets the Sunni guard units, known as Awakening Councils, or Majalis al-Sahwa in Arabic, since they switched sides. His brother was killed on duty last July, then one son was killed by a Yemeni suicide bomber in August.

A second son was slain by a Shi’ite militia in 2005.

Lighting another cigarette, he turned to a window overlooking a square beside a Sunni mosque where Saddam Hussein made his final public appearance in Baghdad in April 2003.

His guards feared the future, Ibrahim said, partly because they no longer had contact with the U.S. military. Many Sahwas fear Baghdad will turn on them for their insurgent past.

“I still have good relations with the United States. I could go and live there,” he said, as a pair of yellow canaries chirped in a small cage and a rickety ceiling fan revolved overhead.

“But I was born here, lived here, and I intend to die here. If I go, others will go, and then who will stay?”