This verse literally starts out with, I also said
(see KJV, NASB). Judges 2:3 is in a certain tension with Judges 2:1. As Michael Wilcox explains, “Judges 2:1 and Judges 2:3 should be read like this: 'I said, I will never break my covenant … and I also said, If you compromise with these nations I will not drive them out'. It is as though the Lord is saying, ‘I have sworn to give you the whole of this land, yet I have also sworn not to give it to a disobedient people.'"1
The angel is recalling words previously pronounced, in Numbers 33:55 and Joshua 23:13. The present tense Now therefore I tell you
is nevertheless appropriate, since the repetition of this warning means it would now be executed.2 The Lord was fulfilling his side of the covenant curse.
3 So now I say, I will not drive them out before you, but they shall become thorns in your sides, and their gods shall be a snare to you.”