Iran has manufactured and delivered to Iraq high-tech bombs that are proving particularly deadly to American soldiers, a senior U.S. intelligence officer said on Sunday.

The officer, briefing reporters on condition he not be identified, alleged that orders to ship such weapons have come from the "highest levels" of the Iranian government.

Between June 2004 and last week, more than 170 Americans have been killed by the bombs, which the military calls "explosively formed penetrators (EFPs)," the officer said.

Thirty-seven American troops have died this month alone, including a soldier who came under small-arms fire northeast of Baghdad on Saturday, the military said.

Officer says components are smuggled

The officer said American intelligence analysts believe the EFPs are manufactured in Iran and smuggled into Iraq on the orders of senior officials in Tehran. He did not elaborate.

The United States has long accused Iran of providing weapons to insurgents in Iraq, but until now, has stopped short of blaming senior Iranian leaders. Tehran has repeatedly denied any involvement in the Iraq war.

The U.S. officer said Iran was working through surrogates — mainly "rogue elements" of the Shia Mahdi Army — to smuggle the EFPs into Iraq.

He said most of the components are entering Iraq near Amarah, the Iranian border city of Meran, and the Basra area of southern Iraq.

The officer said American authorities had briefed Iraq's Shia-led government on Iran's involvement and Iraqi officials had asked the Iranians to stop.

Prime Minister Nouri al-Maliki, a Shia, has said he told both the U.S. and Iran that he does not want his country turned into a proxy battlefield.

Al-Maliki, who has been reluctant to crack down on the Mahdi Army, largely because he does not want to lose the support of its leader, Muqtada al-Sadr, said Iraqi security forces would be deployed this week as part of a U.S.-backed security sweep aimed at stopping the violence in Baghdad.

Last month, U.S. President George W. Bush said he was sending 21,500 additional troops mostly to the Iraqi capital to curb sectarian violence.

As the Baghdad operation begins, U.S. officials have been stepping up allegations that Iran is assisting Shia militias that pose a major threat in the capital and surrounding areas.

Last week, U.S. officials said they were investigating allegations that Shia politician Jamal Jaafar Mohammed, a member of the bloc that brought al-Maliki to power, was a main conduit for Iranian weapons. Mohammed is believed to have fled to Iran.

With files from the Associated Press