Trade friction between the two countries could arise at any time.
Literal
Both-countries [possessive-の] between [in-では] trade-friction [subject-が] whenever arise [even-if-ても] not-strange.
いつ生じてもおかしくない (it wouldn't be strange for it to arise at any time) is a pattern meaning 'could happen at any moment.' 貿易摩擦 (trade friction) is a specific term from international economics. おかしくない (not strange) is a litotes — understating by denying the negative.