Speaking at a press conference in London with Ryan Crocker, the US ambassador to Iraq, General David Petraeus told reporters that he hoped instead that Iran would eventually play a constructive role across the border.

"There is no question about the very lethal and damaging impact of the Iranian activity and support for these militias," Petraeus said on his return to Baghdad after testifying to Congress last week about Iraq's future.

Echoing testimony in Washington, Petraeus said there was clear evidence that Iran was training militias and giving them weapons, including rockets and improvised explosive devices (IEDs) that have killed many allied troops.

When asked about the prospect of US military operations in Iran, Petraeus replied: "I certainly have not sought authorisation to cross the border into Iran. We have our hands full in Iraq."

The four-star general, wearing his green uniform covered in medals, added that US-led coalition forces were focused inside Iraq on blocking the alleged flow of weapons and militiamen heading from training camps in Iran.

"We're waiting to see some reduction in that activity," he added.

In his testimony before Congress on September 11, Petraeus demurred on whether US forces should respond with operations inside Iran.

The general said he was focused on Iraq, and any military operations outside the country were the responsibility of Admiral William Fallon, the commander of the US Central Command.

The US military in July announced the capture in Basra of a senior Hezbollah militant, Ali Musa Daqduq, who it accused of training "special groups" of Shiite militants at camps near Tehran under the auspices of the Iranian Revolutionary Guard Quds Force.

Iran has denied the charges.

Crocker, who also testified to Congress with Petraeus last week, told reporters that he believed that Tehran was divided over whether to support the militias or boost stability within its neighbor to the west.

"The Iranians have a decision to make -- whether their long-term interests override their short-term tactical desire to cause problems for us, us being the coalition," he said. "They really can't have both.

Petraeus said he was due to meet with Britain's Prime Minister Gordon Brown after holding talks here Tuesday with defence officials about the tasks British troops are performing in Iraq as they reduce their presence.

He insisted the alliance remained as strong as ever.

related report
US Defense Department contractors in Iraq
The US Defense Department has 137,000 contractors working for it in Iraq, including 7,300 private security personnel, the US military said Tuesday.

US Defense Secretary Robert Gates is looking into the role of contractors following the killing of 10 people Sunday in an incident involving private security guards protecting a State Department convoy, a spokesman said.

The military's figures, which are compiled on a quarterly basis by the US Central Command, do not include contractors hired by the State Department or other US government agencies in Iraq.

As of July 7 there were 137,000 Defense Department contractors in Iraq, a spokesman for the US Central Command said in an email.

Of those, 7,300 were private security personnel, said Navy Lieutenant Joseph Holstead.

US citizens account for 22,400; 45,100 are third country nationals, and 69,000 are Iraqis, he said.