Gideon Rachman has written a article called "And Now For World Government." Abdu'l-Baha pushed for some form of world government the moment that he got off of the boat in 1912. At that time, reporters asked him why he had traveled from Persia to the United States. Abdu'l-Baha said that he had come to the U.S. to usher in a "universal peace."
On December 5, 1912, the day that he left the United States, Abdul-Baha had this to say:
"These are my final words of exhortation. I have repeatedly summoned you to the cause of the unity of the world of humanity, announcing that all mankind are the servants of the same God, that God is the creator of all; He is the Provider and Life-giver; all are equally beloved by Him and are His servants upon whom His mercy and compassion descend. Therefore, you must manifest the greatest kindness and love toward the nations of the world, setting aside fanaticism, abandoning religious, national and racial prejudice.
The earth is one native land, one home; and all mankind are the children of one Father. God has created them, and they are the recipients of His compassion. Therefore, if anyone offends another, he offends God. It is the wish of our heavenly Father that every heart should rejoice and be filled with happiness, that we should live together in felicity and joy. The obstacle to human happiness is racial or religious prejudice, the competitive struggle for existence and inhumanity toward each other.
Your eyes have been illumined, your ears are attentive, your hearts knowing. You must be free from prejudice and fanaticism, beholding no differences between the races and religions. You must look to God, for He is the real Shepherd, and all humanity are His sheep. He loves them and loves them equally. As this is true, should the sheep quarrel among themselves? They should manifest gratitude and thankfulness to God, and the best way to thank God is to love one another.
Beware lest ye offend any heart, lest ye speak against anyone in his absence, lest ye estrange yourselves from the servants of God. You must consider all His servants as your own family and relations. Direct your whole effort toward the happiness of those who are despondent, bestow food upon the hungry, clothe the needy, and glorify the humble. Be a helper to every helpless one, and manifest kindness to your fellow creatures in order that ye may attain the good pleasure of God. This is conducive to the illumination of the world of humanity and eternal felicity for yourselves. I seek from God everlasting glory in your behalf; therefore, this is my prayer and exhortation. "
Abdu'l-Baha said much more on the day of his departure. The full text can be found in the book THE PROMULGATION FOR UNIVERSAL PEACE.