The peace talks failed again, but both sides blamed the other for the failure.
Literal
Peace-talks [topic-は] again failed but, both-sides together other-party [to-に] failure [possessive-の] responsibility exists [quotative-と] accused.
A complex news sentence. 双方とも ('both sides') uses とも ('both'). 相手方 (あいてがた, 'the other party') is formal vocabulary. 責任ありと非難した packs the accusation's content via quotative と: 'accused, saying responsibility exists.'