President Obama had more stern warnings for Moscow today, saying the United States will take actions to "isolate" Russia if it continues its occupation of Ukraine's Crimean Peninsula.

"If, in fact, they continue on the current trajectory that they're on, that we are examining a whole series of steps - economics, diplomatic - that will isolate Russia and will have a negative impact on Russia's economy and its standing in the world," the president said.

"Over time this will be a costly proposition for Russia, and now is the time for them to consider whether they can serve their interests in a way that resorts to diplomacy as opposed to force," he added.

The president's comments at the White House came as the State Department said it was "likely" that the U.S. would pursue economic sanctions against Russia.

Speaking to reporters during his Oval Office meeting with Israeli Prime Minister Benjamin Netanyahu, Obama reiterated that Russia is violating international law

"What cannot be done is for Russia with impunity to put its soldiers on the ground and violate basic principles that are recognized around the world," he said. "I think the strong condemnation that it's received from countries around the world indicates the degree to which Russia's on the wrong side of the history on this."

The president urged lawmakers to act quickly to pass an assistance package for the Ukrainian government.

"I would hope that that would be the first order of business, because at this stage, there should be unanimity among Democrats and Republicans that when it comes to preserving the principle that no country has the right to send in troops to another country unprovoked, we should be able to come up with a unified position that stands outside of partisan politics. And my expectation is, is that I'll be able to get Congress to work with us in order to achieve that goal," he said.