By David Alexander
WASHINGTON (Reuters) - Iran is directly supporting extremist Shi'ite groups that are killing U.S. troops in Iraq and any agreement to keep American forces there beyond the end of the year would have to address the problem, the top U.S. military officer said on Thursday.
Admiral Mike Mullen, speaking at a luncheon with reporters, said Iranians -- with full knowledge of Iran's leadership -- were providing Iraqi Shi'ite groups with high-tech rocket-assisted weapons and shaped explosives effective at penetrating armor.
"Iran is very directly supporting extremist Shia groups which are killing our troops," said Mullen, chairman of the Joint Chiefs of Staff. "And there's no reason ... for me to believe that they're going to stop that as our numbers come down."
He said Iran made a conscious decision in 2008 to curb its involvement in Iraq, but had now resumed sending supplies to extremist groups, evidently positioning itself to be able to say that it had helped to drive U.S. forces from the region.
"There's no question they want to influence, and particularly in the south," Mullen said. "They are shipping high-tech weapons in there ... which are killing our people and ... the forensics prove that."
Mullen said he believed any agreement to keep U.S. troops in Iraq beyond the end of the year "has to be done in conjunction with control of Iran in that regard." He said Baghdad was aware of U.S. concerns about the issue.
All U.S. troops are scheduled to be out of Iraq by December 31 under a status of forces agreement between the two countries. But discussions are under way that could allow Iraqis to retain some U.S. forces to help in areas such as air defense where they need support.
White House spokesman Jay Carney said earlier this week that the Obama administration would consider any request made by the Iraqis to retain some U.S. troops there beyond the deadline.
He said no request had yet been made and indicated time was running out because Washington had to stay on course for withdrawal if it was to meet the December deadline for pulling out its remaining forces. Mullen said some 46,000 remain in Iraq.
Mullen said discussions were ongoing with the Iraqis about what capabilities were needed and how many personnel.
"The current discussions cover both, and there are very clear capability gaps that the Iraqi security forces are going to have," he said, citing air defense, aviation and elements of intelligence.
(Editing by Eric Walsh)