Norwegian oil company DNO, the first to drill in post-war Iraq, has said it has yet to receive payment for its oil exports from the country.
The payments have stalled as DNO's partner, the Kurdistan Regional Government, and Baghdad argue over how to share the oil revenue.
"There's not much we can do," DNO chief executive Helge Eide said.
The negotiations are being watched by other oil companies interested in investing in Iraq.
Iraq's self-ruled Kurdish region started exporting crude oil to foreign markets in June.
DNO launched export production from the Tawke oil fields on 1 June, ramping up its output to 50,000 barrels per day and exports to 45,000, which is worth some $100m per month.
It said it will export 50,000 barrels per day when its oil is eventually pumped into the Iraq export pipeline system near the Turkish border.
The company could provide no timeframe for when it may receive the payments, but Mr Eide said the Kurdish government said it hoped it would reach a deal soon.
The disagreements over oil contracts are part of a wider dispute between the Kurds and the Iraqi central government over land, power and the country's massive oil reserves.
Iraq has the world's third-largest oil reserves, but only produces up to 2.4 million barrels per day - which is below the level before the US-led invasion in 2003.