By Phil Stewart and Humeyra Pamuk WASHINGTON (Reuters) – Russia has in place about 70% of the combat power it believes it would need for a full-scale invasion of Ukraine and is sending more battalion tactical groups to the border with its neighbor, two U.S. officials said on Saturday. In the last two weeks, the number of battalion tactical groups (BTG) in the border region has risen to 83 from 60 as of Friday and 14 more are in transit, the officials told Reuters on condition of anonymity due to the sensitivity of the information. As to the timing of an invasion, the ground is expected to reac…