By Engen Tham and Julie Zhu (Reuters) – Top Chinese banks are rushing to ensure they can maintain business ties with Russian clients without running afoul of a barrage of Western sanctions, people with knowledge of the matter told Reuters. Western nations are tightening an economic noose around Russia following its invasion of Ukraine, shutting its banks from the SWIFT global financial network and pushing global firms to dump billions in investment. While the Chinese banking regulator said this week the country would not join the West’s sanctions on Russia, some of its banks have stopped issui…