Sen. John McCainJohn Sidney McCainDeclassify the post-9/11 torture program Arizona GOP censures top state Republicans McCain, Flake and Ducey Whoopi Goldberg wears 'my vice president' shirt day after inauguration MORE (R-Ariz.) emphasized Monday that border security must be the top priority right now when it comes to immigration.

McCain joined with his Arizona colleague, Senate Minority Whip Jon Kyl (R), to urge federal authorities to immediately dispatch 3,000 National Guard troops to the border in the wake of the murder of an Arizona rancher in which an illegal immigrant is suspected.

McCain, a longtime advocate of comprehensive immigration reform that includes a path to citizenship for illegal immigrants, said that border security must now be the top priority.

"The lesson is clear: First we have to secure the border," McCain said in a press conference. "If you want to enact some other reforms, how can that be effective when you have a porous border?

"So we have to secure the border first."

McCain's plea comes as he fends off a conservative primary challenge from former Rep. J.D. Hayworth (R-Ariz.). McCain's work on comprehensive reform had sometimes stoked the ire of members of the conservative base of the Republican Party.

McCain and Kyl said they'd been in touch with Homeland Security Secretary Janet Napolitano to fund the troop deployment along the border, suggesting that cuts elsewhere could be made to pay for the plan.

"We will be seeking increases in appropriations, but we will find plenty of money in appropriations to shift from unneeded and unnecessary programs," McCain said.