By Tom Balmforth, Polina Nikolskaya and Steve Holland MOSCOW/DONETSK/WASHINGTON (Reuters) – Western nations on Tuesday punished Russia with new sanctions for ordering troops into separatist regions of eastern Ukraine and threatened to go further if Moscow launched an all-out invasion of its neighbour. The United States, the European Union and Britain announced plans to target banks and elites while Germany halted a major gas pipeline project from Russia, which they say has amassed more than 150,000 troops near Ukraine’s borders. Moscow has denied planning an invasion. One of the worst security…