http://news.bbc.co.uk/2/hi/middle_east/6917648.stmMilitias firing rockets and mortars on Baghdad's heavily protected Green Zone have become more accurate because of training in Iran, the US military says.
The comments were made by Lt-Gen Raymond Odierno, one of the top US commanders in Iraq.
It is the latest in a series of accusations made by the US about the alleged training and arming of Iraqi Shia militiamen by Iran.
The Iranian government has repeatedly denied involvement.
It says it wants stability in Iraq, and blames the violence there on the US-led invasion.
Deadly barrage
"In the last three months, we have seen a significant improvement in the capability of mortar men and rocketeers to provide accurate fire into the Green Zone and other places," Lt-Gen Odierno told a press conference.
"We think this is directly related to training conducted inside Iran," he said.
"One of the reasons why we're sitting down with the Iranian government... is trying to solve some of these problems," he added.