Kirkuk used to pump 40% of Iraq's total production
Oil output has resumed from the giant Kirkuk field in Iraq.
The country's North Oil Company announced on Tuesday that it had restarted the field.
But it said that pre-war output levels would not be reached in the near future because of war damage, looting and a shortage of workers.
The company's deputy director, Adil Qazzazz, told Reuters that oil output resumed last Thursday at 30,000-40,000 barrels per day (b/d).
He said the fuel was being pumped by pipeline to refineries to meet local fuel needs.
Before the war Kirkuk pumped 850,000 b/d, about 40% of Iraq's total production.
"We will not reach our former production levels in the near future," Mr Qazzazz said.
"We have lost lots of equipment and machinery, some was destroyed and some was looted, and we have no transport for workers."
"The US military are trying to help, they are trying to provide the security we need."
Last Tuesday oil production resumed in the southern oil fields.
And US military officials estimated that production in the northern fields could be restored to 800,000 b/d in two to six weeks from 21 April.
Before the war, when UN sanctions were in place, Iraq produced about 2.5 million b/d.
But the country's huge reserves could produce far more.
Mr Qazzazz said the Kirkuk field could produce a million b/d with the right equipment but this would take a "long time".