Ukrainian government forces pressed on with a military drive against pro-Russian separatists on Wednesday as Ukraine, Russia, Germany and France prepared a meeting of foreign ministers to try to bring the crisis in Ukraine's east under control.Rebels fired a shoulder-launched missile that struck and damaged a SU-24 attack plane, a military spokesman said, while one Ukrainian border guard was killed in the early hours in a mortar attack on his post on the border with Russia."The armed forces and the National Guard are continuing the offensive on terrorists and criminals. The actions of our military are effective and are having results," parliament speaker Oleksander Turchynov said.Ukrainian President Petro Poroshenko, under pressure at home to take a forceful line against separatists who have been fighting government forces since April, refused to renew a ceasefire on Monday night and ordered a government offensive "to answer the terrorists, militants and marauders."That move won backing from the United States, but drew criticism from Russian President Vladimir Putin who said the newly-elected Ukrainian leader had veered off the road to peace.Separatism erupted in the Russian-speaking east in April, when rebels seized buildings and strategic points, declaring "people's republics" and saying they wanted union with Russia. As of June 30, a total of 191 Ukrainian service personnel have been killed, including 145 soldiers, Andriy Lytsenko, a spokesman for the national security and defence council, said on Wednesday. Hundreds of civilians and rebels have been killed. In a fresh attempt to stop the spread of the crisis, which has caused the biggest Russia-West confrontation since the Cold War, Russian, Ukrainian, German and French foreign ministers were to meet in Berlin later on Wednesday.Diplomats cautioned against expectations of a breakthrough."There is not a precise objective. It's an opportunity to work on peace efforts, but we don't want to raise expectations," a French diplomatic source said on Tuesday.Russian Foreign Minister Sergei Lavrov had backed the idea of the meeting with France's Laurent Fabius and Ukraine's Pavlo Klimkin during a phone conversation with his German counterpart Frank-Walter Steinmeier late on Tuesday, the Russian foreign ministry said.Poroshenko, who accuses Russia of fanning the conflict and allowing fighters and equipment to cross the border to support the rebels, turned his back on another renewal of a 10-day unilateral ceasefire after phone talks involving Putin, German Chancellor Angela Merkel and French President Francois Hollande.