Bush, after meeting a group of conservative activists, said marriage was exclusive to that of a man and woman.
"Ages of experience have taught us that the commitment of a husband and wife to love and to serve one another promotes the welfare of children and the stability of society," he said. "Government, by recognising and protecting marriage, serves the interests of all."
At the same time Republicans in Congress put forward a bill to ban the burning of the US flag, a plan George Bush senior tried during his time in the White House.
The first unit of 55 national guards soldiers will be arrive at the Mexican border today.