Abadi said in a televised message from New York, where he is attending the United Nations General Assembly, that Iraqi forces would also move to retake two areas in western Anbar province, Reuters reported.
"These operations pave the way for cleansing every inch of Iraqi land and God willing its end will be the liberation of Mosul city, ... the liberation of all Iraqi lands and the end of ISIS," he said.
The regular and volunteer forces had already surrounded the town, where tens of thousands of civilians are believed to have been trapped by Daesh.
Iraq has been facing the growing threat of terrorism, mainly posed by the Daesh terrorist group.
Daesh militants made advances in northern and western Iraq over the summer of 2014, after capturing swaths of northern Syria.
The Iraqi army is gearing up for a major offensive in to purge Daesh from Mosul, the country's second city. Iraqi forces have managed to wrest control of several areas in the southern parts of the city.