Senate negotiators have clinched a deal that would double the number of patrol agents and double the length of fencing along the U.S.-Mexico border, giving the Senate immigration reform bill a major boost.

Sens. Bob Corker (R-Tenn.) and John Hoeven (R-N.D.) announced the agreement Thursday afternoon and predicted it could secure the votes of as many as 15 Republicans for final passage.

The amendment is expected to cost more than $30 billion, and members of the Gang of Eight expressed confidence it would help achieve 100 percent border surveillance and a 90 percent apprehension rate of illegal entrants along the southern border.