Western countries have been rocked by fierce public debate over whether to repatriate their citizens who joined the Islamic State group, which held swathes of Iraq and Syria for years before losing its last speck of land last month.

Around 1,000 suspected foreign IS fighters are in detention in northeast Syria, in addition to around 9,000 foreign women and children in Kurdish-run camps there.

Iraq has proposed trying and sentencing the foreign suspects if the US-led coalition covers operational costs, three Iraqi officials have said.

"These countries have a problem, here's a solution," one told AFP, speaking anonymously because he was not authorised to give details to the press.

The source said Iraq had proposed a rate of $2 million per suspect per year, calculated based on the estimated operational costs of a detainee in US-run Guantanamo.

"We made the proposal last week but have not gotten a response yet," the source added.

A second official said Iraq had requested $2 billion to try the suspects as "one of several options," and could ask for "more money to cover the costs of their detention."

Iraq has already tried and sentenced several hundred foreign IS members, and others are in detention in Baghdad awaiting trial.

They include at least 12 French nationals who were transferred from Syria in February.

A third Iraqi official said detainees from as many as 52 countries could be put on trial in Baghdad.

"Iraq proposed to the coalition setting up a special tribunal to try foreigners. There's been a constructive beginning to those discussions," the source said.

But setting up the court could be complicated, the official said, with questions over whether international funding for it would preclude any implementation of the death penalty.

The source added that Iraq had opted to propose the arrangement to the US-led coalition as a whole because it was simpler than negotiating with each country individually.

The US-led coalition did not immediately respond to an AFP request for comment.

Syria's Kurds have called for an international court in northeast Syria to try IS jihadists, but the US says countries should repatriate their own citizens.

Transferring foreign fighters to Iraq for trial appears to resolve a legal conundrum for Western powers, many of whom fear they may not have enough evidence to convict IS members who claim they did not fight.