Mosul is the largest city under control of the militants who captured it in 2014 to declare a caliphate over vast swathes of regions of Iraq and Syria.
"I can say the battle won't be delayed after the first half of this year, and its end by God's will shall also be swift,'' Obeidi said in an interview in Cairo on Thursday.
"We can determine when the battle starts, but its end depends on variables.''
Iraqi Prime Minister Haider al-Abadi in December said 2016 will be the year of "final victory'' over ISIL.
He spoke after the Iraqi army retook from the militants the city of Ramadi, west of Baghdad.