"Apparently people have forgotten that America, as the most powerful country on Earth, still does not control everything around the world," Obama told White House reporters at a news conference.
"So our diplomatic efforts often take time. They often will see progress and then a step backwards. That's been true in the Middle East. That's been true in Europe. That's been true in Asia. That's the nature of world affairs. It's not neat, and it's not smooth," he said when asked if the United States has lost its influence in the world.
"But what we can do is say to Putin, if you continue on the path of arming separatists with heavy armaments that violates international law and undermines the territorial integrity and sovereignty of Ukraine, then you're going to face consequences that will hurt your country," he said.
"There was a lot of scepticism about our ability to coordinate with Europeans for a strong series of sanctions. Each time we have done what we said we would do, including this week, when we put in place sanctions that have an impact on key sectors of the Russian economy - their energy, their defense, their financial systems. It hasn't resolved the problem yet," he said.
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"That's always been true. That doesn't mean we stop trying. It is not a measure of American influence on any given day or at any given moment that there are conflicts around the world that are difficult," he said.
"I recognise with so many different issues popping up around the world, sometimes it may seem as if this is an aberration or it's unusual. But the truth of the matter is that there's a big world out there, and that as indispensable as we are to try to lead it, there's still going to be tragedies out there and there are going to be conflicts," Obama noted.
"I mean, the fact of the matter is, is that in all these crises that have been mentioned, there may be some tangential risks to the United States. In some cases, as in Iraq and ISIS, those are dangers that have to be addressed right now, and we have to take them very seriously.
"But for the most part, these rockets aren't being fired into the United States. The reason we are concerned is because we recognize we've got some special responsibilities," he said.