Bush spoke at the nation's largest training center for law enforcement.
He chose the get-tough setting as conservative critics blast a Senate proposal as being soft on people who break the law. Hoping to blunt that message, Bush emphasized that any new options for immigrants and foreign workers would not start until tougher security is in place.
The presidential stop came during a congressional recess, with senators back home and facing pressure from the left and right on the immigration plan. Bush's aim is to build momentum for the legislation, perhaps his best chance for a signature victory in his second term. The Senate expects to resume debate on it next week.
"A lot of Americans are skeptical about immigration reform, primarily because they don't think the government can fix the problems," Bush said.
"And my answer to the skeptics is: give us a chance to fix the problems in a comprehensive way that enforces our border and treats people with decency and respect. Give us a chance to fix this problem. Don't try to kill this bill before it gets moving," Bush told students and instructors at the Federal Law Enforcement Training Center.
Bush repeatedly cast the matter as one of political courage.
"Those determined to find fault with this bill will always be able to look at a narrow slice of it and find something they don't like," the president said. "If you want to kill the bill, if you don't want to do what's right for America, you can pick one little aspect out of it.
"You can use it to frighten people," Bush said. "Or you can show leadership and solve this problem once and for all."
The bill would give temporary legal status to millions of unlawful immigrants, provided they came forward, paid a fine and underwent criminal background checks. To apply for a green card, they would have to pay another fine, learn English, return to their home country and wait in line.
The plan also would create a guest worker program. It would allow foreign laborers to come to the U.S. for temporary stints, yet with no guarantee they can eventually gain citizenship.
Both the new visa plan and the temporary worker program are contingent on other steps coming first. Those include fencing and barriers along the Mexico border, the hiring of more Border Patrol agents and the completion of an identification system to verify employees' legal status.
The legislation would also reshape future immigration decisions. A new point system would prioritize skills and education over family in deciding who can immigrate.
Georgia's senators both played leading roles in producing Bush's deal with the Senate. Yet they have also said they may not support the final bill, depending upon how it is amended.
Bush chastised those who say the proposal offers amnesty to illegal immigrants. He called it empty political rhetoric.
