BAGHDAD, June 1 (Reuters) - Iraq, negotiating an agreement on keeping U.S. forces in the country, has sent teams to study military pacts Washington has with other nations, Iraq's Foreign Minister Hoshiyar Zebari said on Sunday.

The United States, which invaded Iraq in 2003 to oust Saddam Hussein, is negotiating an agreement with Iraq aimed at giving a legal basis for U.S. troops to stay in Iraq after Dec. 31, when their United Nations mandate expires.

The "status of forces" agreement is similar to pacts the United States has with many other countries, setting out rules for U.S. military activity.

"Recently, we dispatched ... four tactical teams to visit Germany, Turkey, South Korea and Japan, just to see the way they did their status of forces agreements," Zebari told a news conference with visiting French Foreign Minister Bernard Kouchner.

The situation in Iraq was different because military operations were still going on, he said. Zebari said the agreement was "an Iraqi need" because the country's security forces were not yet self-sufficient.

The United States has around 155,000 troops in Iraq and how long U.S. troops will stay in the country is a big issue in the U.S. presidential election.

The talks have angered many Iraqis who suspect the United States of wanting to keep a permanent presence in Iraq. On Friday, thousands answered a call by anti-American cleric Moqtada al-Sadr to protest against the agreement.

Sadr has called for protests to continue until Prime Minister Nuri al-Maliki's government agrees to a referendum on the U.S. presence in Iraq.

Zebari said Iraq and the United States had achieved a "great deal of progress" both on the forces agreement and on a separate agreement setting out a framework for U.S. diplomatic relations with Baghdad.

However, Iraqi government spokesman Ali al-Dabbagh said on Sunday that talks on the "status of forces" deal were still at an early stage and there were differences between the sides over its content.

"The Iraqi side has a vision and their draft differs from the American side and their vision," he said.

Abdul Aziz al-Hakim, head of the Supreme Islamic Iraqi Council, the biggest Shi'ite group in Maliki's government, has also criticised the planned agreement on a troop extension. (Reporting by Adrian Croft; Editing by Michael Georgy and Catherine Evans) (adrian.croft@thomsonreuters.com; Reuters Messaging: adrian.croft.reuters.com@reuters.net))

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