US Secretary of State John Kerry has called on Russia to defuse the crisis in Ukraine or face additional consequences as a war of words between Washington and Moscow escalates over the eastern European country.The US State Department said on Saturday that Kerry told Russian Foreign Minister Sergei Lavrov in a telephone call to reduce tensions with neighboring Ukraine and pull Russian troops back from the border.Kerry "made clear that if Russia did not take steps to de-escalate in eastern Ukraine and move its troops back from Ukraine's border, there would be additional consequences," a senior State Department official said. On Saturday, a large number of armed men seized government buildings in the eastern Ukrainian city of Kramatorsk, 150 kilometers (90 miles) from the Russian border, and authorities in Kiev called it an "act of aggression by Russia."According to the official, Kerry expressed "strong concern" that attacks by armed men in eastern Ukraine were "orchestrated and synchronized, similar to previous attacks in eastern Ukraine and Crimea." The Autonomous Republic of Crimea declared independence from Ukraine on March 17 and formally applied to become part of Russia following a referendum a day earlier, in which nearly 97 percent of the participants voted in favor of the move.On March 21, Putin signed into law the documents officially making Crimea part of the Russian territory. He said the move was carried out based on the international law. Earlier in the day, Lavrov warned that any military action by the Ukrainian authorities in the eastern parts of the country would undermine diplomatic efforts to resolve the crisis.He said that Russia has no intention to incorporate eastern regions of Ukraine, adding, “We don’t have either our servicemen or our agents there.”“We can have no such intentions. This would run counter to the vital interests of Russia,” Lavrov said.