Around 90 members of the US special forces, part of the 300 military advisors, are already in Iraq and could begin their assessment work this week. Four more teams are expected to arrive in the violence-ravaged country soon.

On Monday, the US and Iraq reached a key agreement on legal protections that would enable up to 300 special operations forces to be deployed in the country.

Kerry arrived in the Kurdish regional capital Erbil Tuesday and went into a meeting with Kurdistan autonomous region President Massoud Barzani to urge the Kurds who are keen to establish their separate state, to help in the political process.

Ahead of going to Erbil, Kerry had a meeting with Iraqi Prime Minister, Nuri Kamal al-Maliki, and Shiite and Sunni politicians.

He assured Kurdish leaders that the imminent deployment of American military forces is "not intervention" in Iraq's affairs.

During the meeting, Barzani is quoted as saying that Kerry was confronting an enormous challenge in seeking a multi-sectarian national government. He stressed, "We are facing a new reality and a new Iraq."

Earlier, he blamed prime minister Nouri al-Maliki's "wrong policies" for the violence and called for him to quit, saying it was "very difficult" to imagine Iraq staying together.

The US top official arrived in Erbil as fighting continued for the control of Iraq's largest oil refinery at Baiji, which is facing sustained onslaught by Islamist militants of the Islamic State in Iraq and the Levant (Isis) backed by disgruntled Sunni tribes.

In an interview with American journalist Andrea Mitchell, Kerry said the US forces would be on an "advisory" mission "planning, advising, some training and assisting" as something short of intervention, since "we are not here in a combat role. We are not here to fight. And the president has no intention none whatsoever of returning American combat troops in Iraq to go back to where we were."

The troops that have arrived are organised into four teams. On Tuesday they began to set up a "joint operations center" with the Iraqi military, Pentagon press secretary Rear Adm. John Kirby said. They join 30 "advisers" already there on secondment from the US embassy, according to the Guardian.

The UN said at least 1,075 people, mostly civilians, have been killed since the insurrection began 17 days ago.

Kurdish troops have taken control of Kirkuk, which was abandoned by the Iraqi army after Isis forces seized Mosul. The Kurds consider Kirkuk just outside their autonomous zone their historic capital.

The Kurdish region is home to vast oilfields and has maintained stability, in contrast to the rest of Iraq.

Kerry said that all the Iraqi leaders agreed to start the process of forming a new government by 1 July, which will advance a constitutionally required timetable for distributing power among Iraq's political Shia and Sunni blocs. Kurds represent about 20 percent of Iraq's population and usually vote as a unified bloc.

A United Nations human rights team in Iraq said that at least 1,075 people have been killed in Iraq so far in June, most of them civilians.

The UN said the figures, which include a number of summary executions, should be viewed as an absolute minimum. >BNN