The Senate has rejected Kentucky Republican Rand Paul’s amendment to hold annual border security votes as part of comprehensive immigration reform by a 61-to-37 vote.

Under Paul’s ‘Trust But Verify” proposal, Congress would be required to vote once every five years to certify the border is sufficiently secure. Specifically, the amendment calls for 95 percent apprehension rate, a double fence on the U.S-Mexico border and full border surveillance.

The Senate is currently debating the so-called ‘Gang of 8’ proposal to overhaul the immigration system, but many conservatives have voiced hesitation unless specific provisions to block illegal immigration at the border are not added.

Paul says he is disappointed in Senate colleagues and indicated the reform efforts may have lost his support.

“I hope Congress can produce immigration reform that actually solves the problems in our current system. Unfortunately, now, the Senate bill does not. I will continue to work to solve our immigration problems,” he says. “I hope I am able to support a good bill, but it is now clear the House will have to lead the way.”

Observers note a handful of prominent GOP lawmakers voted against Paul’s amendment including bill co-sponsors John McCain and Jeff Flake of Arizona, Lindsey Graham of South Carolina, and Marco Rubio of Florida.

In a Tweet after the vote, Paul said those who opposed his proposal were “against securing our border first.”