Iran seems to be honoring a commitment to stem the flow of deadly weapons into Iraq, contributing to nearly a 50 percent drop in the number of roadside bombs that kill and maim American troops, a US general said. Maj. Gen. James Simmons, a deputy commander of Multinational Corps-Iraq, told reporters Thursday that the number of roadside bombs either found or exploded nationwide had fallen from 3,239 in March to 1,560 last month. The October figure was the lowest since September 2005, he said. Simmons said the decline included all types of roadside bombs, including lethal "explosively formed penetrators" - the signature weapon of Shiite extremists that can hurl a fist-sized chunk of molten copper through the thickest US vehicles. US authorities insist penetrator bombs come from Iran, despite Iranian denials.