President Bush is in the American southwest, seeking to win support for his immigration policies in a border region where the issue is hot. Mr. Bush wants to combine tougher enforcement, with a temporary guest worker program.
The president went to the state of Arizona to promote what he called his "comprehensive immigration strategy."
"Illegal immigration is a serious challenge, and our responsibility is clear. We are going to protect the border," said Mr. Bush.
Recent polls show most Americans want stronger action to control U.S. borders. But there is little agreement on how best to meet the challenge of illegal immigration.
In Arizona, where the problem has reached crisis proportions, vigilante groups have sprung up along the border and some conservatives have proposed building a high-tech fence to keep illegal immigrants out.
The president says money has already been approved to bolster the border patrol, and more help is on the way.
"We are going to secure the border by catching those who enter illegally, and harden the border to prevent illegal crossings," added Mr. Bush.
In the southwest, the situation is so serious that the governors of Arizona and New Mexico have declared statewide emergencies. Mr. Bush promised not only more border agents, but steps to streamline deportations of illegal immigrants, fight document fraud, and increase workplace enforcement.
"We want to make it clear that when people violate immigration laws, they are going to be sent home," explained Mr. Bush.
The president's remarks, made to border patrol and customs personnel at an air force base near Tucson, Arizona, focused largely on enforcement, a key concern of his conservative political base. But Mr. Bush also made clear enforcement alone will not solve the problem, and urged support for his proposal to set up a guest worker program which would match undocumented immigrants with U.S. employers who have jobs no Americans will fill.
"Workers would be able to register for legal status for a fixed period of time and then be required to go home," noted Mr. Bush. "This program would help meet the demands of a growing economy and it would allow honest workers to provide for their families while respecting the law."
President Bush first proposed the program in January, saying it would help both foreign workers who need a job and American business-owners who need help. Supporters have said it will also increase national security by easing pressure on the border and freeing law enforcement officers to focus more on would-be terrorists and drug runners.
But some of the president's fellow Republicans have criticized the idea, saying it would amount to an amnesty for illegal immigrants already in the country. Mr. Bush urged the critics to take another look at his proposal.
"The program that I propose would not create an automatic path to citizenship. It wouldn't provide for amnesty," he added. "I oppose amnesty. Rewarding those who have broken the law would encourage others to break the law and keep pressure on our border."
The House of Representatives will vote soon on border enforcement legislation. Senate debate on a broader immigration bill is scheduled to begin in February.