Was the 'river of Egypt' in Genesis 15 the Nile?

According to the explanation, the 'river of Egypt' in Genesis 15 is not the Nile. There was another river a little east of the Nile in that region. The promised land extends from that river of Egypt to the great river Euphrates.

Les explains that in Genesis 15, God appeared to Abraham and transferred the title deed of the land to him, making a covenant. The land promise runs from the river of Egypt to the great river Euphrates. Les does not think this refers to the Nile, because at that time there was another river a little east of the Nile, down in that region. The Euphrates goes through present-day Iraq to the Persian Gulf. This entire area will be Israel's homeland when the Kingdom is set up, because she has never had it yet. David and Solomon got part of it, but not all. The land will cover the whole Middle East, south to the tip of the Red Sea and over to the river of Egypt, by virtue of the tribes listed.

Genesis 15:18

In the same day the LORD made a covenant with Abram, saying, Unto thy seed have I given this land, from the river of Egypt unto the great river, the river Euphrates:

What is the 'river of Egypt' in Genesis 15:18?

In Genesis 15:18 the river of Egypt is not to be identified as the Nile. According to the transcript, at that time there was another river a little east of the Nile, in that same neck of the woods. It marked one boundary of the land promised to Abraham’s seed, extending to the Euphrates.