Immigration reform has been a top domestic priority for President Barack Obama's second term, and immigrant-rights groups have demanded that Congress make changes to legalize undocumented immigrants.
Under the compromise, the government would grant legal status to immigrants living in the United States illegally, but green cards would be withheld until the security steps were complete.
According to ABC News, the so-called "border surge" will call for doubling the size of Border Patrol from its current force of 21,000 and completing the 700-mile border fence authorized by Congress in 2006.
"This is a border surge. We have militarized our border, almost," said Sen. Lindsey Graham, a South Carolina Republican.
The deal also includes the purchase of new surveillance drones to track would-be illegal border crossers.
"Boots on the ground, drones in the air," summed up Sen. Chuck Schumer, the New York Democrat who has been at the center of efforts to push immigration legislation through the Senate.
The cost of the additional agents alone was put at $30 billion over a decade.
Also under the agreement, immigrants would not be able to claim credit for Social Security taxes they paid while working without lawful status, and neither the administration nor states would be permitted to grant welfare benefits for five years to immigrants currently living unlawfully in the U.S.
The plan was announced by Sens. John Hoeven of North Dakota and Bob Corker of Tennessee, Republicans who had been publicly uncommitted on the legislation. Both said other GOP fence-sitters would also swing behind the measure if the changes were incorporated, and by late in the afternoon, two had done so.
A final vote on the legislation is expected by the end of next week. The next move would be up to the House, where majority Republicans are overwhelmingly opposed to granting citizenship to immigrants living in the United States illegally. Talks on any final compromise would be held in the fall - if then.
The Associated Press contributed to this report.