Republicans are heading for a veto showdown with President Obama over an annual defense bill.

Majority Leader Mitch McConnell (R-Ky.) has teed up the Senate to turn to the $612-billion National Defense Authorization Act (NDAA) next week, despite a looming veto threat from the White House.

It’s a familiar scenario for lawmakers. Obama has threatened to veto every defense bill for the past six years, but has never done so. Despite their track record, the administration is stressing that with the bill combining a host of policy fights, from lifting budget caps to closing Guantanamo, the president will hold firm this year.

Speaking to reporters after lawmakers released their conferenced version of the bill, White House Press Secretary Josh Earnest called it an “irresponsible way to fund our national defense priorities,” reiterating that “if the president got this bill he’d veto it.”

Senate Republicans, however, appear poised to try to either the call the president’s bluff or force him to issue his fifth veto on legislation that they argue is vital for helping troops and protecting national security.

Sen. John McCain (R-Ariz.), the chairman of the Armed Services Committee, said Obama vetoing the defense bill would be “shameful.”

“If the President vetoes the NDAA, at this time of mounting global threats, he will be prioritizing politics and process over the security of our nation and the well-being of our armed forces,” he added.

Republicans, including McCain, argue that Obama shouldn’t pick a spending fight over the defense bill, which outlines Pentagon policy but doesn’t appropriate money.

If that fails, the Arizona Republican has given the president a more direct reason not to veto the legislation: A slate of civilian defense nominees need to be approved McCain’s committee, and their fate could rest on Obama’s decision.

But the president is facing pressure to send the defense bill, which could reach his desk by the end of the week, back to Congress.

The policy bill has in many ways turned into a proxy war between Republican lawmakers and the administration over spending. Democrats say an extra $38 billion sought through the overseas contingency operations (OCO) fund is meant to help the Pentagon circumvent congressionally mandated budget caps, and underscores the need for a long-term deal that would increase funding for defense and nondefense programs.

Defense Secretary Ashton Carter is also recommending that Obama veto the bill.