President Obama on Monday said the U.S. was weighing a number of measures to “isolate Russia” if Moscow did not de-escalate the crisis in the Ukraine and end their military intervention.

“What we are also indicating to the Russians is if in fact they continue on the current trajectory they're on, then we are examining a whole series of steps -- economic, diplomatic -- that will isolate Russia and will have a negative impact on Russia's economy and status in the world,” Obama told reporters, ahead of a meeting with visiting Israeli Prime Minister Benjamin Netanyahu at the White House.

“We've already suspended preparations for the G-8 summit, and we would expect there would be further follow-up on that. We're looking at a whole range of issues that John Kerry mentioned yesterday,” he added.

Obama said the international community was “largely united” in accepting that Moscow’s movement of troops into the Crimean peninsula — a region of Ukraine with a large Russian population — is a "violation of international law" and Russia’s own promises.

"What cannot be done is for Russia for impunity put its soldiers on the ground and violate basic principles that are recognized around the world,” Obama said.

Russia moved troops into Crimea over the weekend, claiming they were needed to protect the safety of ethnic Russians in the region. Ukraine is politically divided between a western half that favors closer ties with Europe and an eastern half with historic cultural and economic ties to Russia.

The administration was quick to condemn Russia's actions as a violation of Ukraine's sovereignty and an effort to undermine the interim government which replaced Moscow-backed former President Viktor Yanukovych. But the standoff shows no signs of ending, with Russia insisting they would not pull out their troops.

Reports said Kiev was accusing Russia of delivering a military ultimatum to hand over Ukranian warships in the Black Sea or face a military assault. A report from AFP, however, said Russian military officials were denying that those claims.

Obama said the U.S. understood Russia had longstanding ties to the Crimean peninsula, but that Moscow should work with the international community to address their concerns and insure a stable Ukraine.

“We should be able to set up international monitors and an international effort,” Obama said to mediate. “We should be able to de-escalate the situation.”

The president added that there are “two paths Russia can take.”

"Over time, this will be a costly proposition for Russia," Obama vowed.

Some congressional lawmakers have floated sanctions to punish Russia for its military moves.

Obama on Monday said that the first priority for Congress should be aid to stabilize Ukraine, calling on lawmakers to "work with the administration to provide a package of assistance” for the beleaguered country.

"I would hope that would be the first order of business" Obama said, urging that the issue be "outside of partisanship."

Secretary of State John Kerry will visit Kiev on Tuesday, and Obama said the trip would highlight that the U.S. remains “strongly supportive of the interim Ukrainian government.”

The president said the U.S. would “offer a very specific and concrete package of economic aid.”