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* Sunni tribesmen take control of Jordan-Iraq border crossing
* Jordanian army beefs up border with more troops
* Border crossing remains open despite Iraqi army pullout after brief clashes with rebels
* Jordanian officials say see no immediate threat to kingdom (Adds border open, minister's quote and meeting between local border officials on both sides)
By Suleiman Al-Khalidi
AMMAN, June 23 (Reuters) - Sunni tribesmen took control of a border crossing between Iraq and Jordan after Iraq's army pulled out of the area following clashes with rebels, Iraqi and Jordanian intelligence sources said on Monday.
It was not immediately clear if the tribesmen's seizure of the Turaibil crossing, the only legal crossing point between Iraq and Jordan, late on Sunday was part of the broader advance by Sunni militants led by the Islamic State in Iraq and the Levant (ISIL).
The militants earlier overran posts further north along Iraq's border with Syria, pursuing their goal of forming a "caliphate" straddling both countries that has raised alarm across the Middle East and in the West.
The withdrawal of the Iraqi army from the Turaibil border crossing left it with no presence along the entire western frontier, which includes some of the Middle East's most important trade routes.
Jordanian army sources said their troops had been on a state of alert along the 180-km (112-mile) border with Iraq for several days to ward off "any potential or perceived security threats".
Army units in the desert town of Ruwaished near the Iraqi-Jordanian border crossing and in other army camps in the area were put on a heightened state of alert, an army source said later on Monday.
Witnesses saw dozens of armoured vehicles and scores of tanks on the highway heading to the Iraqi border crossing in what a Jordanian official said were reinforcements "that were sent in the last 24 hours in view of the latest developments".
Minister of State for Media and Communication Mohammad al-Momani told Reuters "the authorities were continuing to beef up defences as a preventive step in view of the security situation which Iraq is passing through."
Truck drivers who crossed the border into Jordan said Sunni tribesmen were now manning checkpoints along large stretches of the Baghdad-to-Amman highway.
The Turaibil crossing remains a major artery for Sunnis in western Anbar province, and in the past two years Shi'ite Prime Minister Nuri al-Maliki has closed it several times while the Iraqi army waged security clampdowns in the region.
A security official who has been in touch with Iraqi customs and local staff said the crossing was being operated by the bulk of the usual staff. They had been instructed by the Sunni tribal militants, who are now in charge of the desolate desert area, to keep it running.
Reflecting the growing sectarian nature of the conflict, senior Shi'ite officials fled with the Iraqi army after the attack by Sunni tribal militants, leaving matters in the hands of Sunni employees, according to an Iraqi source familiar with developments at the border crossing.
A Jordanian security source confirmed the Jordanian border post chief met with his Iraqi counterpart and agreed to keep the crossing open for traffic. The border crossing was quiet although a few trailers passed through, officials said.
Other witnesses who had come from the border earlier said Sunni tribal militants had not entered the border post with their men or vehicles but were manning checkpoints almost 35 km away, closer to the town of Rutba, 145 km east of the border with Jordan.
An Iraqi Sunni tribal leader in Anbar province who was involved in taking over of the border crossing, told Reuters by phone that his group had no interest in disrupting trade with Jordan.
"This crossing is a vital lifeline for our people in Anbar who get goods and food from Jordan, and we don't have an interest in scaring anyone by getting rid of the local officials and running it directly," he said.
Many Sunni Iraqis from major tribes in Anbar have extensive ties with Jordan, where many of their wealthy kin have taken refuge and have set up large investments following widespread alienation of their community by the new Shi'ite leaders of Iraq after the end of the U.S. occupation.
Gains by ISIL - considered the most powerful force among armed groups who seized the Iraqi city of Falluja, west of Baghdad, and took parts of Ramadi, capital of the western Anbar province, at the start of the year - have helped it secure supply lines to Syria, where it has exploited the chaos of the uprising against President Bashar al-Assad to seize territory.
Jordanian officials say the loss of Iraqi government control over the border crossing was not seen as an immediate security threat to the kingdom, although many within its political establishment were unnerved by the prospect of al Qaeda-affiliated groups along the border. (Additional reporting by Oliver Holmes in Baghdad; Editing by Janet Lawrence and Ken Wills)