In the background of the US nuclear talks with Iran in Oman, the US has given Iraq permission to transfer $2.7 billion to Iran, despite the sanction restrictions. The money is meant to cover Iraq’s debt to Iran for supplying them with gas and electricity, according to a Walla report.
Sounds like sanctions. If Iraq does business with a sanctioned country, US relations with Iraq would be damaged. So it’s not like the US is the middleman here, but more that Iraq wants to maintain good relations with the US and thus will work within the US’ sanctions.