Bush has signed a controversial new bill to build a fence along the US-Mexico border to stem the flow of illegal immigrants.
Mr Bush approved the fence despite strong opposition from Mexico, whose government has warned the barrier would "damage" bilateral relations.
In signing off the $US1.2 billion ($A1.6 billion) package, the Mr Bush said the bill will modernise border protection by adding fencing, vehicle barriers, infrared cameras and ground-based radars.
"That's what the people of this country want. They want to know that we're modernising the border so we can better secure the border," he said.
The new measures form part of a $US33.8 billion ($A45.3 billion) Homeland Security funding bill that includes money for immigration measures.
But the money approved for border measures falls well short of the cost of the 1,100 kilometres of fencing required along the border as approved by Congress last week.
It approved the barrier – which would cover approximately one third of the entire length of the US-Mexico border – despite estimates such a fence would cost up to $US6 billion ($A8 billion) to construct.