The rare talks in Baghdad were narrowly focused on Iraq's spiralling sectarian violence and did not touch on Iran's controversial nuclear programme, which has ratcheted up tensions between the two arch foes in recent months.

"Positive" was how both sides characterized the four-hour meeting that began with a handshake between US ambassador to Iraq Ryan Crocker and his Iranian counterpart Hassan Kazemi-Qomi at Iraqi Prime Minister Nuri al-Maliki's office in Baghdad.

The Iranians appeared keen for further talks, with Kazemi-Qomi calling the meeting "a first step in negotiations between these two sides" and saying Tehran would seriously consider an Iraqi invitation for further discussions.

For his part, Mr Crocker said he had been less interested in arranging further meetings than laying out Washington's case that Shi'ite Iran is arming, funding and training Shi'ite militias in Iraq, a charge Iran denies.

Kazemi-Qomi, speaking at a separate media conference several hours later, said Iran also saw positive steps in the talks. He said Iran had offered to help train and arm Iraq's security forces, presently the job of the US military.

The meeting marked a shift in the US policy of shunning almost all contact with Iranian officials since Washington severed formal diplomatic ties with Tehran in 1980, 14 months after Iran's Islamic Revolution and five months after Americans were seized in a hostage crisis at the US embassy in Tehran.