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BAGHDAD, July 2 (Reuters) - Senior Iranian leaders know about the operations of Iran's Revolutionary Guards Qods Force in stirring up violence in Iraq, the U.S. military said on Monday.

The U.S. military has long accused the Qods Force of arming and training Iraqi Shi'ite militants who attack U.S. and Iraqi soldiers. Iran has repeatedly denied involvement in violence in Iraq and blames the U.S.-led invasion in 2003 for the bloodshed.

"Our intelligence reveals that senior leadership in Iran is aware of this activity," U.S. military spokesman Brigadier-General Kevin Bergner told a news conference in Baghdad, in some of the most direct accusations yet about how much Tehran's government knows of such operations.

"We also understand that senior Iraqi leaders have expressed their concerns to the Iranian government about the activities."

Iran does not officially acknowledge the existence of the Qods Force. Military experts and some exiled Iranians say it is a wing of Iran's ideologically driven Revolutionary Guards that operates abroad. They say it reports directly to Iran's top authority, Supreme Leader Ayatollah Ali Khamenei.

The Revolutionary Guards have a separate command structure to Iran's regular military.

Bergner also said the Qods Force was working with the Lebanese Shi'ite militia group Hezbollah to carry out acts of violence in Iraq.

He said the United States had discovered the existence of three relatively small camps located close to Tehran where Iraqi Shi'ite militants were being trained. Between 20-60 militants were receiving training at any given time, he said.

Iran's government had done little to help improve security in Iraq, he added.

"We have not seen the demonstrable improvement or anything that could be accounted for as a change in behaviour on the part of the government of Iran in reducing these threats and reducing the levels of violence," Bergner said.

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