D.C., June 13, 2007 (AP): Republican and Democratic senators working to save President Bush's stalled immigration bill are focusing on toughening border security and workplace enforcement to attract more bipartisan support.

Negotiators also were considering harsher penalties for immigrants who overstay their visas or re-enter the country without documentation, according to Sen. Lindsey Graham, R-S.C.

``If you had mandatory jail time'' for such offenses, Graham said, ``I think it would create a deterrent.''

Another possible amendment, he said, would prohibit employers from participating in a new temporary worker program if they repeatedly break the law by hiring undocumented workers.

An amendment by Sen. Kay Bailey Hutchison, R-Texas, would require all undocumented immigrant household heads to return to their countries of origin before obtaining legal status. Under the legislation, only those seeking green cards—permanent legal residency—would be required to return home first.

With senators maneuvering behind the scenes to try to craft a comprise package than can win passage, it is not clear when the measure will come up again for formal Senate floor debate.

Bush’s bill that could grant eventual citizenship to millions of undocumented immigrants was derailed in the Senate last week in the face of broad Republican opposition. One of his top domestic priorities, the president made a rare visit to the Capitol on Tuesday to meet with Senate Republicans and try to revive the measure.

Lawmakers told the president that the American public has little faith that the government can secure the nation's borders or weed out undocumented workers at job sites, according to participants at the closed-door meeting. They spoke on condition of anonymity.

To alleviate such concerns, Bush said he was receptive to an emergency spending bill as a way to emphasize his administration's commitment to accelerated enforcement. One congressional official put the price tag at up to $15 billion.

``It's a highly emotional issue,'' the president said after attending a weekly Senate Republican luncheon.

``I don't think he changed any minds,'' conceded Sen. Mel Martínez, R-Fla., a supporter of the legislation.

But Martínez added that the president's appearance had helped nudge “people on the fence'' to be more favorably inclined.

Bush administration officials also weighed in, with Homeland Security Secretary Michael Chertoff telling skeptical conservatives in a letter that manpower and money would be committed to improving border security and enforcement.

``Failure to act on this legislation will deny the country the safety and security provided by these enhanced enforcement measures,'' Chertoff wrote Tuesday night.

Many conservative Republicans have criticized the measure as an amnesty for millions of lawbreakers. Additionally, job approval ratings in the 30 percent range make it difficult for the president to bend even Republican lawmakers to his will.

Apart from the additional funds, Republican and Democratic supporters of the bill hoped to complete work on an agreement that could free it for final passage by month's end.

Senate Majority Leader Harry Reid, D-Nev., said it was up to Bush and the Republicans to produce enough votes to revive the measure.

``We'll move on to immigration when they have their own act together,'' Reid told reporters.