Abadi told a cabinet meeting that "talks have been going on for the past year to gradually reduce the number of the (coalition) forces" from the current figure of roughly 10,000.

The US-led coalition said on Monday it was "adjusting" its force levels in Iraq downwards as it shifts away from combat operations against the Islamic State group.

It gave no details but made clear the focus would now be on consolidating military gains against IS after more than three years of fighting in Iraq and Syria.

The Iraqi prime minister said the threat from IS was not over.

"There is still a danger inside Syrian territory. We control the borders, but there could be a real danger," said Abadi.

"We need significant air cover to monitor the desert and terrorist movements. We need efforts from the coalition and... want to do a fully successful job," he said.

In December, Iraq declared victory against IS, more than three years after the extremist group seized a third of its territory and swathes of neighbouring Syria, declaring a "caliphate" ruling over millions of people.

Formed in October 2014, the US-led coalition brought together 50 countries in the fight against the jihadist group. It now includes 74 countries and works with NATO and Interpol.

The United States deployed about 2,000 soldiers in Syria and more than 5,000 in Iraq.

At the end of November, it announced the withdrawal of 400 Marines from Syria.