The leaders of the UK, Germany, France and Italy are expected to press Mr Putin to do more to end the fighting.They accuse Russia of arming separatist rebels and sending regular Russian troops to Ukraine. Moscow denies this.Ukraine and the rebels agreed a truce in September, but each side accuses the other of repeated shelling.The separatists control parts of Ukraine's Donetsk and Luhansk regions.More than 3,500 people have been killed since the fighting erupted in April, following the annexation by Russia of Ukraine's southern Crimea peninsular a month earlier.Putin's warningMr Putin will hold a meeting with Mr Poroshenko on the sidelines of the Asia-Europe (Asem) summit in the northern Italian city.The carcasses of a destroyed aeroplane at Donetsk airport. Photo: 16 October 2014Across the table from him will also be UK Prime Minister David Cameron, French President Francois Hollande, German Chancellor Angela Merkel and Italy's PM Matteo Renzi.President Poroshenko met Ms Merkel ahead of Friday's talks, with both expressing regret that many points of a peace plan agreed last month in the Belarusian capital Minsk "had not yet been implemented", German government sources were quoted as saying by the AFP news agency.Russian media quoted Kremlin spokesman Dmitry Peskov as saying that there were still "serious differences" between the two leaders over the origins of the crisis.Ms Merkel said it was "first and foremost" Russia's responsibility to make sure the peace plan was being followed.Among other points, the plan envisages the withdrawal of heavy weaponry 15km (10 miles) by each side from the line of contact and the withdrawal of all foreign mercenaries from the conflict zone.Earlier this week, Mr Putin ordered the withdrawal of nearly 18,000 Russian troops stationed near the Ukrainian border.However, Nato says it has seen no sign of any major Russian pullback.Gas concernSpeaking ahead of the Milan talks, Mr Putin stressed that he would not be blackmailed by the EU and US over the Ukrainian crisis.In what was seen as a direct reference to US President Barack Obama, the Russian leader warned of "what discord between large nuclear powers can do to strategic stability".With European sanctions imposed on his country and relations at their lowest ebb since the end of the Cold War, Mr Putin is unlikely to find a particularly warm welcome in Italy, the BBC's Damian Grammaticas in Milan reports.The likely response from his European counterparts is that the sanctions will not be lifted until they see real changes on the ground, our correspondent says.In Milan, Mr Putin is also expected to discuss Russian gas supplies to Europe. Most of the gas is delivered via Ukraine.The Russian president has already warned that Europe faced "major transit risks" unless Ukraine settled its gas row with Moscow.Russia cut gas supplies to Ukraine in the summer, accusing Kiev of failing to pay its debts. Ukraine says the price set by Moscow is unfair.The two-day Asem summit brings together more than 50 member states.(BBC)Bakudaily.Az