Washington ? Senators pushing a new immigration policy appealed Sunday to wavering supporters ahead of renewed debate on securing the borders and dealing with 12 million undocumented immigrants.

A fragile compromise was pulled from the Senate in early June, then resurrected after bipartisan negotiations with the White House. The bill awaits a crucial test vote this week. With several senators distancing themselves from the proposal, the outcome was too close to call.

“We’ll see if between the two parties we have 60 votes” needed to keep the bill moving toward a final vote, said Sen. Dianne Feinstein, D-Calif.

The measure would tighten borders, require workplace verification and create a guest worker program. It also would lay out a way for the estimated 12 million people illegally in the U.S. to gain legal status and work toward citizenship.

President Bush long has advocated an immigration overhaul. On Saturday, he urged lawmakers to “summon the courage” to support what could be the last major legislative achievement of his presidency. “The status quo is unacceptable,” he said in his weekly radio address.

But he faces dissension from fellow Republicans who demand better border security and oppose any policy that suggests amnesty for undocumented immigrants.

On the other side of the aisle, Democrats have taken hits from their normal allies, including labor and some Hispanic groups. They say the proposal is bad for workers or that provisions for obtaining visas place too much emphasis on skills, to the disadvantage of family ties.