President Obama vetoed a sweeping $612 billion defense policy bill Wednesday in a rebuke to congressional Republicans, and insisted they send him a better version that doesn't tie his hands on some of his top priorities.

In an unusual veto ceremony, Obama praised the bill for ensuring the military stays funded and making improvements on military retirement and cybersecurity. Yet he pointedly accused Republicans of resorting to "gimmicks" and prohibiting other changes needed to address modern security threats.

"Unfortunately, it falls woefully short," Obama said. "I'm going to be sending it back to Congress, and my message to them is very simple: Let's do this right."

The rare presidential veto marked the latest wrinkle in the ongoing fight between Obama and Republicans who control Congress over whether to increase federal spending — and how.

Four years after Congress passed and Obama signed into law strict, across-the-board spending limits, both parties are eager to bust through the caps for defense spending. But Obama has insisted that spending on domestic programs be raised at the same time, setting off a budget clash with Republicans that has yet to be resolved.

To side-step the budget caps, known in Washington as sequestration, lawmakers added an extra $38.3 billion to a separate account for wartime operations that is immune to the spending limits. The White House has dismissed that approach as a "gimmick" that fails to deal with the broader problem or provide long-term budget certainty for the Pentagon.

Obama also rejects the bill as written due to provisions making it harder for him to transfer suspected terror detainees out of the military prison in Guantanamo Bay, Cuba, a key campaign promise that Obama is hard-pressed to fulfill before his term ends. The White House has also expressed concerns over provisions preventing military base closures and funding equipment beyond what the military says it needs.

But Republicans lambasted Obama for prioritizing the domestic spending he seeks over the security of U.S. troops and the nation they protect.

"This is the worst possible time for an American president to veto their national defense bill, and especially to do so for arbitrary partisan reasons," Senate Majority Leader Mitch McConnell said on the Senate floor.

The veto forces Congress to revise the bill or try to settle the larger budget dispute. Although Republicans have vowed to try to override Obama's veto, the White House insisted it was confident it had the votes to ensure Obama's veto stays in place.