President Viktor Yushchenko has signed the order for withdrawing Ukraine's troops from Iraq, the head of the country's security council said Tuesday _ cementing a pledge by the new leadership to bring back its 1,650-strong force. Ukraine began pulling out its servicemen from Iraq last week and plans to complete the withdrawal of its troops by the end of the year. The ex-Soviet republic provided the sixth-largest contingent in the U.S.-led coalition in Iraq. Eighteen Ukrainian soldiers have been killed in Iraq and more than two dozen have been wounded, fueling public dismay about the unpopular deployment. More than 130 soldiers returned home last week, and Ukraine plans to withdraw an additional 550 soldiers from Iraq by May 15 and the rest of the original contingent by the end of the year, the Defense Ministry has said. The head of Ukraine's National Security and Defense Council, Petro Poroshenko told a news conference Tuesday that in a formal move the president had signed an order making the withdrawal irreversible. "The president has signed the plan for a staged withdrawal of our peacekeeping contingent from Iraq," Poroshenko said. "The plan is a very carefully crafted document which details the terms of the Ukrainian pullout from Iraq." The end date for the pullout will be "fixed after consultations with the other coalition members" and the Ukrainian contingent is likely to leave Iraq in November or December, Poroshenko said. The troop pullout was one of the new president's campaign promises. Ukraine strongly opposed the U.S.-led war but later agreed to send a large contingent to serve under Polish command in central and southern Iraq. --more 1453 Local Time 1153 GMT