Defense Secretary Leon E. Panetta said Sunday that weapons supplied by Iran are behind a rash of attacks against American forces in Iraq, part of an escalating campaign of violence ahead of the planned U.S. troop withdrawal by the end of the year.
"We're seeing more of those weapons going in from Iran, and they've really hurt us," said Panetta, who arrived in Baghdad on an unannounced visit after a two-day stop in Afghanistan.
U.S. officials said 15 U.S. troops were killed in June, the most in any month in two years. More than half of the deaths were caused by rockets, known as improvised rocket-assisted mortars, that U.S. officials say are provided to Shiite Muslim militant groups by Iran.
A senior U.S. official said the attacks on U.S. forces were an effort by the Iranian-backed militias to make it appear as though they were forcing out American troops, all of whom are due to withdraw by the end of the year under a 2008 agreement between Washington and Baghdad.
Adm. Michael G. Mullen, chairman of the Joint Chiefs of Staff, and other U.S. officials have also said publicly in recent days that Iran is behind the surge in violence against the 46,000 U.S. troops remaining in Iraq.
The high-level effort by the Obama administration to blame Iran for the attacks comes as U.S. officials are stepping up the pressure on Iraqi Prime Minister Nouri Maliki to resolve whether he will ask for some American troops to remain beyond the year-end deadline.
By playing up the Iranian threat, U.S. officials may be hoping to spur such a request from Iraq.
Panetta said he would encourage Maliki when they meet to decide whether Iraq would make a formal request for a contingent of U.S. troops to remain. U.S. officials have signaled for months that they would look favorably on such a request, saying Iraq's military remains unprepared to handle the full range of threats the country faces without continuing American training and assistance.
The idea of keeping any U.S. forces remains deeply controversial in Iraq, where Maliki faces pressure from hard-line members of his Shiite-dominated governing coalition not to extend the American presence.
The participation of anti-U.S. Shiite cleric Muqtada Sadr's movement in Maliki's government is complicating Iraqi forces' ability to go after all the hard-line Shiite groups. Sadr's Promised Day Brigade militia, which opposes the American presence, has political backing.
Extending the U.S. troop presence also would be unpopular with some supporters of President Obama, who had pledged to abide by the timetable for withdrawing U.S. forces.
U.S. officials have refused to say publicly whether they favor keeping troops in Iraq, even though privately some administration officials said that the White House had decided it could keep a force of as many as 10,000. But such a move could be unpopular at home, especially with some Democrats in Congress who have called for a complete pullout, other than a few hundred military personnel who would remain in Iraq to handle arms sales and other routine matters.
Asked Sunday whether he supported keeping American forces in Iraq, Panetta replied: "I think it's really dependent on the Iraqis. If they make the request, I do believe we ought to seriously consider it."
He also said he would urge Maliki to break a logjam that had left the country without defense and interior ministers since last year.
Panetta's four-day swing through Afghanistan and Iraq is his first overseas trip since taking over the Pentagon this month, and it has given him a crash introduction in the difficulties still confronting the U.S. in the two war zones that have consumed the Pentagon's attention for nearly a decade.
Times staff writer Ned Parker contributed to this report.