Tony Blinken, President Barack Obama's deputy national security adviser, said Sunday that a Russian threat to cease inspections of nuclear weapons as required by U.S.-Russian arms control treaties would be "a serious development." Blinken said on NBC's "Meet the Press" that he'd seen news reports of those Russian threats — made in response to U.S. sanctions and other penalties for Russia's seizure of the Crimea region of Ukraine — but that the Russian government had not communicated directly to the Obama administration on that matter. Asked what Obama had accomplished so far in his efforts to deter or penalize Putin, Blinken said the president has been "mobilizing the international community in support of Ukraine to isolate Russia for its actions in Ukraine and to reassure our allies and partners." Blinken said Obama has invited Ukrainian Prime Minister Arseny Yatsenyuk to the White House on Wednesday to consult with him and to demonstrate U.S. support. Blinked argued that the decline in value of the Russian ruble and the increased uncertainty about foreign investment in Russia are "exacting a real cost and a real consequence" for Putin's decision to intervene in Crimea. Russian parliamentary leaders signaled Friday that Russia is prepared to annex Crimea. A referendum will be held in Crimea on March 16 to decide whether the region should join Russia or remain part of Ukraine. But Blinken said if the result of the referendum is that Crimea joins Russia, then "we won't recognize it, and most of the world won't, either."