torontodailynews- - US President George W. Bush has signed legislation to build 700 miles of fence along the US-Mexican border to prevent illegal immigration.

This election-year move against illegal immigration is believed to be aimed at helping Republicans.

"We have a responsibility to secure our borders. We take this responsibility seriously," Bush said in a signing ceremony in White House.

Bush had failed attempt to persuade the US Congress to support a guest worker program for illegal immigrants.

Republicans in charge of the US House of Representatives insisted on border enforcement only, as Americans in Southern states were upset about the impact of illegal immigration.

The 700 miles of fencing would run along parts of four southwestern states, California, Arizona, New Mexico and Texas.

The U.S.-Mexican border runs about 2,000 miles.

In his remarks, Bush said Americans must face the reality that millions of illegal immigrants already live in the US.

Mexico was understandably angry about the fence law. Mexican President-elect Felipe Calderon had said the move would "enormously complicate" relations with the United States.