President Bush says it is time for Congress to enact comprehensive immigration reform.  Mr. Bush devoted his weekly radio address to the subject, which has provoked intense debate and massive demonstrations across the country, and revealed rifts within the president's Republican Party.

It is a polarizing question: how to curb illegal immigration and what to do with the estimated 11 to 12 million illegal aliens already living in the United States.

Last Monday, President Bush addressed the nation on the subject, and has since visited the U.S.-Mexico border to highlight his plan to fix America's immigration system. To date, the House of Representatives has passed a bill that focuses on tough border enforcement. But the Senate has yet to enact a comprehensive measure.

In his weekly radio address, President Bush urged the Senate to act by the end of the month, and encouraged the two chambers to resolve differences between their bills, so that final legislation can be signed into law.

"Congress is now considering legislation on immigration reform," said Mr. Bush.  "That legislation must be comprehensive.  All elements of this problem must be addressed together, or none of them will be solved at all."

President Bush's proposal calls for deploying National Guard troops along the vast U.S.-Mexico border, and using advanced technology to monitor the border region. The plan also calls for a guest worker program, cracking down on employers who hire illegal aliens, and providing a rigorous path to eventual citizenship for immigrants who have led productive lives in the United States.

Congressional critics, mostly within his Republican Party, say any path to citizenship amounts to amnesty for immigrants who broke the law by entering the country illegally. President Bush disagrees.

"There's a rational middle ground between automatic citizenship for every illegal immigrant and a program of mass deportation," he added.  "Illegal immigrants who have roots in our country, and want to stay, should have to pay a meaningful penalty, pay their taxes, learn English, and work in a job for a number of years.  People who meet these conditions should be able to apply for citizenship. But, approval will not be automatic, and they will have to wait in line behind those who played by the rules, and followed the law."

In the Democratic Party response, California Representative Mike Honda called on President Bush to confront conservative Republicans who want to designate illegal immigrants as felons, and criminalize those who aid them. The House bill would do just that.

"The president has failed to lead, failed to take a clear position, failed to secure our borders, and stood on the sidelines while his Republican Party has raised harsh anti-immigrant rhetoric and moved to divide the American people for political gain," said Mr. Honda.  "As the Senate continues to consider comprehensive immigration reform, the president needs to stand up to the far-right [conservative Republicans]."

The immigration debate is playing out against the backdrop of campaigning for congressional elections in November. President Bush hopes to unite his party, and to show results on important issues to the American people.