In a sign of how critical a new border security agreement could be toward securing more Republican support for immigration reform, Sen. Mark Kirk (R-Ill.) now plans to vote for the immigration bill because of a deal expected to be announced later Thursday.

Sen. Mark Kirk (R-Ill.) (AP)

Senators are set to unveil an agreement that will almost double the number of federal agents along the U.S.-Mexico border, require construction of 700 miles of border fencing and provide money for aerial drones in order to bolster southern border security. The changes would need to occur before eligible immigrants could begin applying for permanent legal status.

Kirk said in a statement Thursday that the deal "will restore the people’s trust in our ability to control the border and bring 525,000 people in Illinois out of the shadows. Once the Senate adopts our amendment, I will be proud to vote for a bill that secures our border and respects our heritage as an immigrant nation."

Aides said Kirk is also supportive of the bill because the new agreement includes his proposal to grant citizenship to any immigrant who earns a Combat Infantry Badge in the U.S. military.

Expect to hear from other like-minded Republicans throughout the day Thursday.

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