President Obama's senior adviser said Sunday's referendum vote in Ukraine's Crimea region on whether to join Russia is illegal and that sanctions against Russia will be announced "in the coming days."
Dan Pfeiffer said that the White House is concerned about the referendum, in which Crimea's majority ethnic Russian population is expected to favor annexation. Pfeiffer reiterated calls on NBC's "Meet the Press" that the United States would not recognize the results.
"We are putting as much pressure as we can on the Russians to do the right thing," Pfeiffer said. "They know there are costs to their action here."
Pfeiffer also said the White House is closely watching Russian President Vladimir Putin's moves in eastern Ukraine, as some have suggested Russia is looking at a possible invasion there.
"We're looking at all ways of assistance," Pfeiffer said, though he dodged a specific question about offering military aid. "Everything the Russians have done this far is in violation of international law."
Russian forces seized a gas plant in Ukraine near the Crimea border on the eve of the referendum, causing some to fear Putin has designs on asserting control of more of the country.
Sen. Jeff Flake, R-Ariz., who recently returned with a congressional delegation from Ukraine, said sanctions must come fast to blunt the potential for such an invasion.
"We've got to move in hard now with sanctions regardless of whether they move tomorrow, or the next week or hold back," Flake said on "Meet the Press."