President Bush pressed a passionately divided Congress on Thursday to reach election-year compromise on immigration legislation that provides a chance at citizenship for millions of illegal immigrants already in the country.

With his speech before business leaders and members of a government-sponsored civilian volunteer group, Bush hoped to build momentum for Senate and House negotiators to resolve difficult disputes. The two houses have passed sharply different versions of the legislation. To achieve one of his top domestic priorities of the year, Bush will have to bring around conservatives in his own party.

"It's a difficult task," Bush pointedly told Congress in remarks at the U.S. Chamber of Commerce. "Yet the difficulty of this task is no excuse for avoiding it."

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The House bill generally is limited to border enforcement, making all illegal immigrants subject to felony charges and cracking down on employers who hire illegals. The Senate version includes more money for border security, creates a guest worker program to bring in new foreign workers, and provides a shot at citizenship for many of the estimated 11 million illegal immigrants already in the country.

"The American people expect us to meet our responsibility and deliver immigration reform that fixes the problems in the current system," Bush said. "All of the elements of this problem must be addressed together, or none of them will be solved at all."

Bush also will travel to several cities next week — Artesia, N.M., Laredo, Texas, and Omaha, Neb. — to pitch his immigration approach, the White House announced Thursday.

There is skepticism that a compromise can be reached in a year when most of Congress is up for re-election, and many believe Republicans could be at risk of losing their control over one or both chambers.

The president sought in his speech to provide a roadmap to lawmakers on the negotiating teams. He spoke more specifically about legislative provisions that he supports than he has previously.

He said any measure must include a temporary worker program and the opportunity for eventual citizenship. The Chamber has supported Bush's approach, which would provide cheap labor for many jobs.

Though Bush acknowledged that illegal immigration has put pressure on U.S. schools and hospitals, spawned more crime and caused other problems, he also stress immigrants' importance to American society and the practical benefits of establishing a guest worker program.

"They are part of American life and they're vital to our economy," he said. "And yet they're beyond the reach and protection of American law."

He took on — albeit gently — those in the Republican Party who advocate a get-tough-only approach and staunchly oppose either a guest worker program or a path to citizenship.

"Some members of Congress argue that no one who came to this country illegally should be allowed to continue living and working in our country, and that any plan to allow them to stay equals amnesty, no matter how many conditions we impose," Bush said. "Listen, I appreciate the members that are acting on deeply felt principles. I understand that. Yet I also believe that the approach they suggest is wrong and unrealistic."

The president ticked through other provisions he considers crucial for a bill to be effective.

He asked Congress to provided additional funding and the legal authority to end "once and for all" the country's much criticized "catch and release" policy, in which illegal immigrants from countries other than Mexico are ticketed and freed. He said the practice has been ended for key Central American countries, but additional detention space and legal changes are needed to expand that.

Bush also embraced several changes that would make it easier for employers to verify that their workers are legal, including:

—Allow immigration officials to be notified when an employer is notified by the Social Security Administration that the name of one of their workers does not match the worker's Social Security number.

—Require that all employers use a now-optional government program called Basic Pilot to verify employees' Social Security numbers and check them against other federal databases. Both the House and Senate bills include such a requirement

And he endorsed stiffer penalties for companies that fail to check an employee's identification and knowingly hire an illegal immigrant. "We're not going to tolerate it in this country," the president said.