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Improvised rocket assisted munitions made in Tehran, favored by the Iranian trained Shia militias in Iraq, are placed on the back of flatbed trucks. Their target: U.S. military personnel and their bases in Iraq as the remaining U.S. forces prepare to leave the nation by the end of December.

Fifteen Americans were killed in June, the deadliest month for U.S. personnel serving in Iraq in more than two years. And some say Iranian influence is showing up more and more in attacks on troops in Iraq and Afghanistan.

“You can clearly see what they are doing in Iraq,” Sen. Lindsey Graham, R-S.C., said of Iran in an interview with Fox News. “They are supplying Shia militias in Iraq and trying to disrupt our operations there and claiming that we were driven out.

Graham added that the threat is growing and has become a focal point of U.S. leadership in Iraq.

“Our military commanders in Iraq are very worried about Iranian influence growing in Iraq,” he said.

Today in Baghdad Iraq's Prime Minister welcomed Iran's vice president and 170 Iranian companies who came to lobby for lucrative business contracts. Just a day earlier, U.S. Ambassador Jim Jeffrey on a trip to open the new U.S. consulate in Basra warned that U.S. commanders are seeing more lethal and accurate weapons flowing into Iraq from Iran.

That is a view echoed by Senator Joe Lieberman, I-Conn., who just returned from Afghanistan Tuesday.

“They've got the blood of a lot of people on their hands, including hundreds of Americans who have been killed in Iraq, as a result of Iranian training and equipping of extremists militias,” he said.

But the number two U.S. military commander in Afghanistan would not say publicly that the amount of Iranian weapons in Afghanistan was spiking.

“That level is just about the normal level of arms and ammunition that crosses borders in this volatile region each year, said Lt. Gen. David Rodriguez, Commander of International Security Assistance Joint Force Command. “And they... have not increased significantly in the past two years."

One telling example of the weapons flow from Iran to Afghanistan happened in February, when British troops intercepted a large shipment of 122 millimeter rockets coming produced in Iran. The rockets have a range of about 13 miles, twice the range of what the Taliban was previously using.

Despite Rodriguez’s claims of an insignificant increase, behind closed doors U.S. commanders told a different story to visiting senators on a recent trip to Afghanistan.

“I did receive information that weapons were coming out of Iran to help the Taliban at a crucial moment in Afghanistan,” Graham said.

As the resident hurries to bring 33,000 troops home from Afghanistan in the next year, in Iraq the Obama administration is indicating it would like to leave 10-thousand troops in place, despite the current agreement which calls for all forces to leave by the end of the year. Right now there are 46,000 troops in Iraq.

But so far Iraq's Prime Minister has not made any request. And Wednesday, he was busy meeting the Iranians.

Fox News Pentagon producer Justin Fishel contributed to this report.