defence official = defense official 国防部官员
defence: chiefly British variant of "defense"
all but is an adverb means
1. (of actions or states) slightly short of or not quite accomplished; "the car all but ran her down"
同义词、近义词 - about, almost, most, nearly, near, nigh, virtually, well-nigh
但是国防部官员几乎排除了出兵(的可能性)。
提问者对于答案的评价:多谢。。