A division among Senate Republicans over a guest worker program for illegal immigrants has delayed debate over immigration reform in the U.S. Senate. Lawmakers hope to begin work on the issue later this week.

Senate Majority Leader Bill Frist, a Tennessee Republican, as early as Wednesday is expected to introduce a border security bill that is to be the basis for debate on immigration reform.

In an unusual move, Frist is circumventing legislation approved and sent to the full Senate by the Judiciary Committee on Monday.

The committee bill, which would also step up border enforcement, would establish a temporary guest worker program and offer a path to permanent residency and eventual citizenship for undocumented workers - provisions backed by President Bush.

But the guest worker proposal, which is not included in Frist's legislation, is dividing Republicans.

Senator Lindsey Graham of South Carolina says the program must be included in any immigration reform bill to deal with the reality of an estimated 11 million illegal immigrants in the United States.

"I do not believe it is in our national interest to do border security only," said Lindsey Graham, "That is to me a cop-out [evasion]."

But Senator John Kyl of Texas says the program amounts to an amnesty, and is unfair to others around the world who have been waiting patiently for their turn to become U.S. citizens legally.

"There are literally millions of people around the world who would like to come here," said John Kyl. "They are abiding by the rules, standing in line. For those who say we are going to make the illegal immigrants here get in line, remember the line is in Russia, or China or Mexico or El Salvador. The line is not here in the United States where all of these folks would be permitted to stay.

Judiciary Committee chairman Arlen Specter, a Pennsylvania Republican, will be allowed to introduce his panel's legislation with its guest worker provisions as an amendment to Frist's bill. If the amendment is approved, it would supersede Frist's legislation.

The issue of a guest worker program is a troublesome one for Republicans. The conservative base of their party opposes the plan, but many businesses rely on undocumented workers. In addition, Republicans do not want to alienate a growing and increasingly influential Hispanic electorate this congressional election year.

Democrats, for their part, generally support a guest worker program.

Once the Senate approves an immigration reform measure, it will have to be reconciled with a House-passed bill, which does not contain any guest worker proposal.