(Refiles to correct Donbas typo) By Robin Emmott BRUSSELS (Reuters) -Russia is likely to launch a new offensive in Ukraine’s eastern Donbas region in the next few weeks, NATO Secretary-General Jens Stoltenberg said on Tuesday, adding that allies had time to help prepare the Ukrainian military. Speaking a day before NATO foreign ministers gather in Brussels to discuss more financial, military and humanitarian support for Ukraine, Stoltenberg said Russia was planning a “very concentrated” offensive. “We now see a significant movement of (Russian) troops away from Kyiv to regroup, re-arm and re-s…