The fact that God cannot fail, lie, sin, change or deny Himself does not in the least diminish His sovereignty. Nor is He any the less sovereign because He cannot force anyone to love Him or to receive the gift of eternal life through Jesus Christ. They must be given freely from God's heart without any reason other than love, mercy and grace. Wonderfully, in His sovereign grace, God has so constituted man and has so designed a gift that man may receive it voluntarily by an act of his will and respond in love to God's love. Without a free will man could not receive the gift of eternal life, thus God could not give it to him.
Freedom is a condition of love.
It is impossible that the power of choice could challenge God's sovereignty since it is God's sovereignty which has bestowed this gift upon man and set the conditions for both loving and giving. Power and love do not belong in the same discussion. Thus for mankind to have been given by God the power to choose to love Him or not and to receive or to reject the free gift of salvation, far from denying God's sovereignty, is to admit what God's sovereignty itself has lovingly and wonderfully provided. May we willingly respond from the heart to His love with our love, and in gratitude for His great gift proclaim the good news to others. 4 Augustine, The City of God, V. 10.