* Iraqi government reinforces troops

* Army says targeting "outlaws, criminal gangs"

* Bush urges Britain to keep forces in Iraq

By Haider al-Nasrallah

AMARA, Iraq, June 15 (Reuters) - Iraq's government beefed up army and police units in the southern city of Amara on Sunday for a new crackdown on Shi'ite militias, witnesses said.

Convoys including armoured vehicles and tanks were moving through the northern side of the city, said a Reuters reporter.

The operation, which officials say will start on Thursday, is the latest stage in Prime Minister Nuri al-Maliki's drive to stamp his government's authority on areas previously controlled by Shi'ite militias or Sunni Arab insurgents.

Army Major-General Tareq Abdel Wahab, leader of the security operation, told Reuters that government forces had a list of hundreds of "outlaws, criminal gangs and those who violate security" it would hunt down.

Amara is a stronghold of Shi'ite cleric Moqtada al-Sadr, who agreed to a ceasefire after U.S.-backed Iraqi forces launched a major offensive on his Mehdi Army militia in Basra in March.

Past U.S.-led military operations in the area have targeted militants smuggling weapons from nearby Iran.

Perceived by some as lacking the resolve and charisma needed to stabilise Iraq, Maliki has gained respect at home and abroad with security offensives that have helped reduce violence to the lowest level in over four years.

Success in Amara could boost Maliki's image ahead of provincial elections, due on Oct. 1, seen as the battleground for a power struggle that could redraw Iraq's political map.

Apart from taking on Sadr's fighters, Maliki has made substantial gains against al Qaeda, which U.S. and Iraqi officials say is on the run in Iraq.

"The operation in all of Maysan province will impose the law and regain prestige for the state as we did in Basra," Defence Ministry spokesman Mohammed al-Askari told reporters.

While Iraqi military officials reviewed last-minute plans, the impoverished residents of Amara feared for the worst.

"We are very scared of this operation because the battle will destroy the town. Most people won't leave their houses," said Hassan Hameed, 35, a day labourer.

"We will not accept the targeting of the Medhi Army because they provide people with services."

The Iraqi-led operations underscore the Shi'ite-led government's desire to take more control of security from the 150,000 U.S. troops in the country.

A Defence Ministry spokesman said Iraq would take security responsibility for the southern province of Qadisiya from U.S. forces in July. The province, relatively quiet in recent months, would be the 10th of Iraq's 18 provinces to return to Iraqi control. A U.S. military spokesman declined comment.

LAST CHANCE

U.S. President George W. Bush urged British Prime Minister Gordon Brown on Sunday not to set a timetable for the withdrawal of troops from Iraq.

He said in an interview with Britain's Observer newspaper that the United States and Britain, Washington's main ally on Iraq, both obviously wanted to bring their troops home but this could only be "based upon success".

"Our answer is: there should be no definitive timetable," said Bush, adding he was "appreciative" that Brown was in frequent touch about "what he and his military are thinking".

The newspaper described Bush as issuing a warning to Brown, but the White House dismissed that tone, saying there was no disagreement between the United States and Britain on Iraq.

Only about 4,200 British troops are still in Iraq, most of them stationed at a base in the south. They are the largest foreign military contingent in Iraq after U.S. forces.

Britain has indicated it could pull all forces out by the end of the year, but with the situation still unstable that appears unlikely.

In a statement read on state television on Saturday night, Maliki said he was giving outlaws and criminals a last chance to surrender and hand over weapons in four days in Maysan province.

Checkpoints have been set up on streets in Amara, the regional capital, 300 km (185 miles) southeast of Baghdad.

Helicopters dropped leaflets urging city residents to stay home. Violence is not the only worry for the city's mostly impoverished 250,000 people.

Amara is one of Iraq's poorest regions despite its oil reserves. "As soon as the Iraqi army enters the city, the price of food will rise," said Aqeel Jabir, 30.

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