President Barack Obama has vetoed the military funding bill passed by Congress, envisioning almost $1 billion in aid to Syrian rebels and the Ukrainian government.

As the primary reason for vetoing the House Resolution 1735, as the 2016 National Defense Authorization Act is known, Obama cited the allocation of $38 billion into a war fund not subject to budget caps, saying it “irresponsibly” ducks the spending caps established by the 2011 Budget Control Act. He has called on the Republican-controlled congress to abolish the caps and increase government spending on both military and domestic programs.

"I’m going to be sending [the NDAA] back to Congress. And my message to them is very simple: Let’s do this right," Obama said.

"We’re in the midst of budget discussions -- let’s have a budget that properly funds our national security as well as economic security."

Pres Obama in the process of signing veto on 2016 #NDAA. Back in the House for an override vote on Nov. 5. Not sure numbers are there. — Daniel Wilson (@dwilsonreporter) October 22, 2015

Another point of contention is Subtitle D of the bill, with provisions making it nearly impossible to shut down the detention camp in Guantanamo Bay.

"Let’s make sure that, in a responsible way, we can draw down the populations in Guantanamo, make sure that the American people are safe, and make sure that we’re not providing the kinds of recruitment tools to terrorists that are so dangerous," Obama said.

READ MORE: Pentagon funding bill on Obama’s desk: $600 mln to Syrian rebels, $300 mln to Kiev

The harmonized version of the NDAA passed in the Senate with a veto-proof majority on October 7, but the GOP did not have enough votes in the House of Representatives to override the presidential veto.

Obama’s veto comes as the attention of the public is focused on Democratic frontrunner for the 2016 presidential nomination, Hillary Clinton, testifying before a House committee on Benghazi that took place during her term as Secretary of State.

In signing veto message, Pres Obama says Defense Authorization "falls woefully short" in funding, reform & Gitmo. pic.twitter.com/TCbmaHzoRD — Mark Knoller (@markknoller) October 22, 2015

Among the appropriations in the final version of the bill was a $600 million allotment to train and equip the “moderate” rebels in Syria, and $300 million in military aid to the US-backed government in Ukraine, including “Lethal assistance such as anti-armor weapon systems, mortars, crew-served weapons and ammunition, grenade launchers and ammunition, and small arms and ammunition.”

The NDAA has been vetoed four times in the past 53 years, but always over discrete provisions – sections of the bill that could be amended or removed, so that the revised bill could be approved by the White House in short order. Obama’s objection to the Overseas Contingency Operations (OCO) fund is fundamental to the 2016 bill, and there is no easy way to remove it even if the GOP lawmakers wanted to.

Republicans were quick to criticize the president. Senator John McCain (R-Arizona) called Obama’s veto “reckless, cynical, and downright dangerous.”

4/4 As we prepare to override veto, I urge Congress to do what Obama did not - put interests of troops & nat’l security ahead of politics — John McCain (@SenJohnMcCain) October 22, 2015

“At a time when crises around the world have never been greater, and when U.S. global leadership has never been weaker, this veto will only intensify the challenges we face while putting vital missions in danger,” he added.