Secretary of State John Kerry warned the U.S. and its allies will pursue a "serious series of steps" against Russia if a referendum on Crimea's status goes forward as planned this weekend.
Kerry told the Senate Appropriations Committee on Thursday that he spoke to Russian Foreign Minister Sergei Lavrov that morning before the two top diplomats meet Friday in London. Lavrov is meeting with Russian President Vladimir Putin and his national security team in Sochi today to discuss their response to the U.S. demands that they resolve the crisis in Ukraine by pulling back from the referendum on Crimea's status.
Kerry said he won't know how the situation will further develop until he meets with Lavrov in London tomorrow. The secretary of state decried the referendum, saying there is no justification or legality for it to take place.
Kerry repeated his argument that a hastily assembled referendum, held while thousands of Russian troops occupy Crimea, will not be much of a referendum.
The secretary also said the European community will meet on Monday, and that Obama had indicated he has a strong list of sanctions at the ready in the event that diplomacy doesn't break the stalemate over Ukraine and the Russian incursion into Crimea.
NBC News' Andrea Mitchell contributed to this report.