Baghdad , Iraq ( CNN ) Joint Iraqi forces have started what they believe will be the conclusive push to retake the Iraqi city of Tikrit from ISIS , a paramilitary force participating in the offensive said Tuesday . The forces have started `` the decisive operation '' to liberate Tikrit just over a week after the overall operation began , advancing toward the city from several directions , according to a statement from the predominantly Shiite paramilitary force Hashd Al-Shaab . ISIS was n't making it easy , however . The Sunni extremist group blew up a key bridge near Tikrit , preventing the joint Iraqi forces from using it to cross the Tigris River to approach the city from the east . Iraqi Prime Minister Haider al-Abadi ordered Iraqi forces on March 1 to retake Tikrit and Salahuddin province . Tikrit , best known to Westerners as the birthplace of former Iraqi dictator Saddam Hussein , fell in June to ISIS , which has captured parts of Iraq and Syria for what it says is its Islamic caliphate . In the past few days , forces progressed roughly 50 miles ( 80 kilometers ) down one road toward the city and , by Monday , were about a mile from its center . ISIS fighters have retreated toward the city center from frontline positions , Hashd Al-Shaab 's media office said Tuesday . Al-Shaab 's forces appear to be leading the fight for Tikrit , with support from the Iraqi army and Sunni tribesmen . Also assisting is Iran , which has provided advisers , weapons and ammunition to the Iraqi government . According to the Pentagon , there may be Iranians operating heavy artillery and rocket launchers as well . There have been several failed attempts to recapture Tikrit since the second half of 2014 . If Iraq regains control of the city , it could mean that retaking Mosul -- a city 10 times bigger -- is possible . The Tikrit offensive involves around 30,000 fighters . CNN 's Jason Hanna contributed to this report from Atlanta .
A major offensive for the city was launched just over a week ago . ISIS forces are retreating toward the center of Salahuddin province , says a Shiite force participating in the offensive .