It began with chocolates but now Moscow has tightened checks on all imports from Ukraine in what some say is an attempt to dissuade its neighbor from turning towards Europe and away from its former Soviet ally. Russian President Vladimir Putin has pressed his idea of forming an economic union to reunite part of the Soviet Union, but Ukraine has resisted becoming a member of the Eurasian Union, preferring to keep the possibility of EU membership open. After visiting Ukraine last month, Putin left empty handed, failing to persuade President Viktor Yanukovich to rethink his European move. Shortly afterwards, Russia barred confectionery imports from Ukrainian firm Roshen on health concerns. On Wednesday, Russian border guards started new, and time-consuming checks on all Ukrainian cargos, whether it be ferrous metals, heavy machinery or chemicals. A spokesman for Russia Railways said almost 1,000 rail cars were stuck at the border between the two countries. "As customs servicemen started to carry out more careful checks of cargoes coming from Ukraine, a number of rail cars have amassed near Russian border stations," he said, adding Russian trains bound for Ukraine were also stuck in the congestion. Ukrainian producers, such as the country's largest steelmaker Metinvest, said they had started to feel the impact and that the tighter border checks were already hurting their operations. A spokesman for Russia's Federal Customs Service declined to comment, while his Ukrainian counterpart said the situation at the border was "normal". Ukrainian politicians said the motivation behind the new rules was obvious, part of a pattern in deteriorating ties between the two neighbours over the country's orientation, trade and differences over gas prices. "The ban on the imports of Ukrainian goods into Russia is nothing else but pressure by Russia in order to force Ukraine to join the Customs Union," Arseny Yatsenyuk, leader of opposition party Batkivshchyna (Fatherland), said in a statement. It is not the first time the Kremlin has tried to pressure Ukraine by using trade. Moscow has often hinted that Ukraine's demands for Russia to lower what it called "exorbitant" gas prices would be met if it joined the Eurasian Union. The two countries have waged two "gas wars" in the winters of 2006 and 2009, with Moscow halting deliveries not only to Ukraine but to the rest of Europe, forcing many in the European Union to try to find alternative sources of energy. Kiev's planned agreements on free trade and political association with the European Union, which it hopes to sign in November, will rule out the possibility of a trade deal with the Russia-led trade bloc. "It is widely known that the deals with Ukraine, including the one on gas, rest purely on Kiev's attitude towards Europe," a government source in Moscow said. (Reuters)