Republicans in Congress have often tangled with President Obama over the best strategy for missile defense, which in turn has complicated the funding.

In 2009, Obama introduced a missile defense plan curbing the development of long-range U.S.-based interceptors to deter attacks from places like North Korea. Instead, he put more focus on the more immediate threat of shorter-range Iranian missiles, which could be intercepted over Europe.

GOP lawmakers say this leaves America vulnerable and vowed in their Pledge to America to protect the continental U.S.

"There is real concern that while the threat from Iranian intercontinental ballistic missiles could materialize as early as 2015, the government's missile defense policy is not projected to cover the U.S. homeland until 2020. We will work to ensure critical funding is restored to protect the U.S. homeland and our allies from missile threats from rogue states such as Iran and North Korea,” the pledge states.

A complicating factor is Russia, which strongly opposes the U.S. enhancing its defense systems in Europe.

"Russia doesn't like that we have these systems and that we're putting them in Europe because they could potentially be used to counter Russia's missile forces,” said Todd Harrison, a senior fellow with the Center for Strategic and Budgetary Assessments. "I don't know if technically that is true or not. We say that these systems are only intended for an Iranian threat.”

That dispute boomeranged to the domestic front in March 2012 when a hot microphone caught Obama telling Russian President Dmitry Medvedev that he would have more "flexibility” in negotiations after the November election. Republicans, pounced, saying it proved Obama was willing to make concessions that could undermine U.S. security.

Despite the disagreements, missile defense consistently receives billions of dollars every year, and the level hasn't varied much under Obama.

"We still spend about $10 billion a year on missile defense,” Harrison said. ‘We just spend it on different systems.”

For spending in 2013, Republicans raised the stakes, passing a defense budget in the House that includes $100 million to begin building an East Coast missile defense base base that even military leaders say is not needed now. The Senate hasn't voted on the bill, and Obama has threatened to veto it.

Republican lawmakers are keeping up their efforts to fund the type of missile defense system they think is necessary, with little success so far. But overall, missile defense continues to be a priority and is supported with billions of dollars annually. We rate this a Compromise.