President Bush vowed today to step up enforcement of U.S. immigration laws on America's borders and inside the country, but he said this could not be done without also creating a new "temporary worker program" that would allow illegal immigrants to live and work in the United States for a defined period.

In a speech in Tucson, Ariz., to a gathering of federal Customs and Border Protection personnel, Bush promoted his plan for "comprehensive immigration reform," a proposal that has aroused sharp opposition from elements of his own party. Some Republicans view his guest worker program as a de facto amnesty for illegal immigrants. Bush today reiterated his strong rejection of this characterization and said he would never sign an amnesty into law.

"The American people should not have to choose between a welcoming society and a lawful society," Bush said at Tucson's Davis-Monthan Air Force Base. "We can have both at the same time." He arrived in Arizona after spending the Thanksgiving holiday at his ranch in Crawford, Tex., and he plans to continue promoting his immigration proposals during a visit Tuesday to El Paso, Tex.

Bush, whose approval ratings on his handling of immigration have been in decline, spoke out more forcefully against illegal immigration today than he has in the past, telling his audience that the influx of illegal border-crossers harms the nation.

"As a former governor, I know that enforcing the law and the border is especially important to the communities along the border," Bush said. "Illegal immigration puts pressure on our schools and hospitals. I understand that. I understand it strains the resources needed for law enforcement and emergency services. And the vicious human . . . smugglers and gangs that bring illegal immigrants across the border also bring crime to our neighborhoods and danger to the highways."

Outlining his strategy, Bush said, "We're going to secure the border by catching those who enter illegally and hardening the border to prevent illegal crossings. We're going to strengthen enforcement of our immigration laws within our country. And together with Congress, we're going to create a temporary worker program that'll take pressure off the border, bring workers from out of the shadows, and reject amnesty."

He also called on Congress to "correct weak and unnecessary provisions in our immigration laws," such as a requirement for the government to "release people caught crossing our border illegally if their home countries do not take them back in a set period of time."

In addition, Bush criticized a federal practice of releasing non-Mexican illegal immigrants who are caught crossing the border from Mexico.

"The problem is that our detention facilities don't have enough beds, and so about four of every five non-Mexican illegal immigrants we catch are released into society and asked to return for a court date," he said to laughter from the audience. "When the date arrives, about 75 percent of those released don't show up to the court. . . . This practice of catch and release has been the government's policy for decades. It is an unwise policy, and we're going to end it."

Touting his temporary worker program, Bush said it would "create a legal way to match willing foreign workers with willing American employers to fill jobs that Americans will not do." Under his plan, undocumented foreigners would be allowed to get three-year work visas that they could extend for an additional three years. They would then be required to return home for a year before they could apply for a new work permit.

Critics, including some Republican lawmakers, have denounced this as a backdoor amnesty and said it would reward illegal immigration while doing nothing to curb new influxes. An estimated 10 million to 12 million illegal immigrants live in the United States at present, a number that has burgeoned since a 1986 amnesty that was intended to solve the problem of illegal immigration. Nearly 3 million illegal aliens were granted legal status under the 1986 amnesty.

Bush argued today that his plan "would also help us relieve pressure on the border by creating a legal channel for those who enter America to do an honest day's labor." He said it would "reduce the number of workers trying to sneak across the border" and "free up law enforcement officials to focus on criminals, drug dealers, terrorists and others that . . . mean to harm us."

Bush indicated he realizes that his plan is controversial. "But people in this debate must recognize that we will not be able to effectively enforce our immigration laws until we create a temporary worker program," he said. He pledged that "for the sake of justice and for the sake of border security, I'm not going to sign an immigration bill that includes amnesty."

Recent polls have provided the president with little comfort as he pursues his plan. A USA Today/CNN Gallup poll earlier this month showed that 65 percent of Americans disapprove of his handling of the immigration issue.

A Fox News/Opinion Dynamics poll last month found that 78 percent of voters think the federal government is not doing enough to secure the country's borders. A CBS News poll in October reported similar findings. It showed that 75 percent of adults believe the United States is not doing enough to keep illegal immigrants from crossing into the country. Among Republicans, 87 percent felt that way, according to the poll.