The October figure was the lowest since September 2005, he said. Simmons said the decline included all types of roadside bombs, including highly lethal “explosively formed penetrators” – the signature weapon of Shiite extremists – which can hurl a fist-size chunk of molten copper through the heaviest armor on U.S. vehicles. U.S. authorities insist penetrator bombs come from Iran, despite Iranian denials. Earlier this month, Defense Secretary Robert Gates said Iranians had apparently assured the Iraqi government that it would stop the flow into Iraq of bomb-making materials and other weaponry. “We believe that the commitments that the Iranians have made appear to be holding up,” Simmons said, adding that Iranian-made weaponry still found in Iraq appeared to have been smuggled in months ago. After the news conference, Simmons told The AP that the Iranian move followed “a significant amount of negotiations.” Last week, the Americans freed nine Iranians detained in Iraq for months on suspicion of smuggling weapons to Iraqi Shiite groups. The release was seen as a possible response to Iran’s move to curb weapons shipments. Nevertheless, Shiite militants remain a major threat to U.S. forces in the Baghdad area, despite recent improvements in security in the capital. Shiite extremists were believed responsible for a deadly attack Wednesday against a U.S. Stryker vehicle, which was hit by what Simmons called “an array” of penetrator bombs near an entrance to the Green Zone. One American soldier was killed and five were wounded, the military said. Iraqi police said two Iraqi civilians also were killed.160Want local news?Sign up for the Localist and stay informed Something went wrong. Please try again.subscribeCongratulations! You’re all set! BAGHDAD – Iran seems to be honoring a commitment to stem the flow of deadly weapons into Iraq, contributing to a more than 50percent drop in the number of roadside bombs that kill and maim American troops, a U.S. general said Thursday. The comments by Maj. Gen. James Simmons marked rare U.S. praise for Iranian cooperation in efforts to stabilize Iraq. Washington has repeatedly accused the Islamic republic of aiding Shiite militias and trying to foil U.S. goals in Iraq and the region. But it remains unclear why Iran may have decided to choke off the suspected weapons pipeline. One possibility is that Iran – the most populous Shiite nation – is seeking to shore up the struggling government of Prime Minister Nouri al-Maliki, a Shiite, in the belief it will help Tehran’s long-term interests. Simmons, a deputy commander of Multinational Corps-Iraq, told reporters that the number of roadside bombs either found or exploded nationwide had fallen from 3,239 in March to 1,560 last month.