英文問題:withallbigcountries - 社會議題

BBC environment analyst Roger Harrabin says the declaration is a significant step, with all big countries rich and poor agreeing there is a scientific limit on the amount we should warm the climate.
這對是從BBC網站copy下來的, 其中with all big countries rich and poor agreeing .... 我不知如何解析它的文法, 以至於整據話看起來怪怪的, 所以想請教各位高手協助指點迷津, 謝謝