Washington ? The Senate, nearing completion on an immigration overhaul, on Monday strongly endorsed President Bush’s plan to deploy the National Guard to the U.S.-Mexico border.

By an 83-10 vote, senators approved an amendment by Sen. John Ensign, R-Nev., that sets parameters for the use of 6,000 National Guardsmen in support of the Border Patrol. Troops would be excluded from “search, seizure, arrest or similar activity” and tours of duty could not exceed 21 days.

With Senate leaders pressing for completion of the immigration bill by week’s end, senators were on the floor for an infrequent Monday voting session. In other action, they rejected a measure that critics said could have resulted in wages as low as $3 an hour for farm workers.

Sen. Saxby Chambliss, R-Ga., said his amendment would have brought fairness for the 1.5 million illegal immigrants working in agriculture by establishing a local, occupation-specific wage for them. Farmers who rely on illegal labor have an unfair advantage over those who hire foreigners legally through an agriculture worker program, he said.

“This amendment is simply about fairness,” Chambliss said, adding that it would bring parity for workers already in the agriculture program as well as those who’d gain work visas under the Senate bill.

But Sen. Edward Kennedy, the Massachusetts Democrat who has had a major hand in shaping the sweeping immigration compromise, denounced the proposal.

“They will be treated the same, but they’ll be treated mightily shabbily,” Kennedy said, charging that pay rates could plummet to $3 or $4 an hour.

On a 50-43 vote, the Senate shelved the Chambliss measure.

Though the fragile bipartisan coalition backing the bill has held through contentious votes last week, the unity will be tested anew this week with challenges from the left and the right.

Sen. Kay Bailey Hutchison, R-Texas, will propose a guest-worker program that requires immigrants to return home at the end of their visa. That competes with the temporary worker program in the bill, which would permit workers to apply for legal permanent residence and citizenship.

And Sen. Dianne Feinstein is challenging a key underpinning of the Senate bill, seeking to offer an “orange” card with a path to eventual citizenship for most illegal immigrants here as of January.

The Senate bill would deny legal status to illegal immigrants here two years or less – as many as 2 million people.

“You’re going to find 2 million people? I think that’s very difficult to do,” the California Democrat said, describing her measure as a common-sense solution.