Jews have never claimed such an expanse. It is figurative language about Eretz Yisrael being between the two major empires.
The borders claimed are roughly the land of Canaan, as in Genesis chapters 10, 14, 17, etc.
I believe it is Gen. 15 that God established the “land grant” part of covenant with Abraham. I didn’t look it up so I may be wrong. I was intentionally literal. It is as good of a reason for annexation than any claim the so called Palestinians have. The West Bank is certainly between the Nile and Euphrates. I believe in the God of Abraham, so there is also that element.