At a news conference at the Nuclear Security Summit in The Hague, President Obama was pressed on the effectiveness of his response to Russia's invasion of Crimea. Jonathan Karl of ABC News asked Obama whether he is "concerned" that American influence is declining. He also asked whether Mitt Romney had a point when he called Russia the top "geopolitical foe" of the U.S.

Obama: 'Much More Worried About Nuclear Attack on NYC' Than Russia

The president said throughout history there are examples of countries not doing what the U.S. wants, but he said his administration is standing for the principles that America believes in. He also maintained there is "precedent" for not using military force against Russia in this instance.

"The truth of the matter is that the world's always been messy. What the United States has consistently been able to do, and we continue to be able to do, is to mobilize the international community around a set of principles and norms. And where our own self-defense may not be involved, we may not act militarily. That does not mean that we don't steadily push against those forces that would violate those principles and ideals that we care about," he said.

Watch the question and answer in the two videos below.

On whether U.S. power is declining

On Mitt Romney

Prior to that, President Obama was asked what assurances he could give to the people of eastern Ukraine and other Baltic states that "they will not be next" for Vladimir Putin. He repeated that the international community does not recognize the annexation of Crimea, but "obviously the facts on the ground are that the Russian military controls Crimea."

Obama said the international community must "stay unified" against the Russia's actions. He added that the U.S. opposes Russia's apparent efforts at "intimidation" by amassing troops on the border of eastern Ukraine, but does not believe another Russian invasion is imminent.

"I don't think it's a done deal and I think that Russia's still making a series of calculations," said Obama.

Watch the full response below: