I'm thankful for your concern for your friend's spiritual condition. Jesus wept over the spiritual deadness of the people of His day, and we ought to have the same concern for those around us who reject Christ or do not know Him (see Luke 19:41-42).
You've probably already said almost everything you can say to your friend; he may even be on his guard against any attempts to lecture him or preach to him. Pray, therefore, that God will give you wisdom about this. As the Bible says, there is both "a time to be silent and a time to speak" (Ecclesiastes 3:7). Most of all, pray for your friend, because only God can make him open to Christ.
Remember, too, that our lives often speak louder than our words. Your example of love and patience could do much to help him realize that the Gospel is real, and that God loves him in spite of his rebellion.
It occurs to me, however, that if God opens the door for you to talk further with him about his spiritual condition, you might ask him something like this: "If Jesus walked into the room right now, what do you think He'd say to you?" His answer might be "off the wall" (as we say) -- but it might not. Instead, it might reveal that he's finally beginning to think about God and eternity. It also might give you an opportunity to tell him what Jesus really would say -- that He loves your friend, and wants him to be with Him in Heaven forever.