The Bible does declare there is only one God the Father yes. Not only in John 17:3 but elsewhere such as 1 Cor 8:6.
But keep in mind, the Bible also calls Jesus "God" in Hebrews 1:8 and Isaiah 9:6.
So what do you do now? Are there two gods? But I thought the Shema which Jesus agreed with in Mark 12:29 says there is only one God?