Martino told reporters Italy will withdraw 300 troops, which will decrease its military contingent to 2,600.
Italian Prime Minister Silvio Berlusconi said last month that all the troops will be withdrawn from Iraq by the end of 2006 in coordination with the Iraqi government.
Italy, which has the fourth-largest foreign contingent in Iraq, faces a general election next April where the Iraq war might become an issue. Most Italians and all opposition parties were opposed to the troop deployment.
The Italian government started withdrawing its forces in September, pulling an initial 300 soldiers from Iraq.