U.S. Secretary of State John Kerry urged Russia to abandon the proposed referendum on the annexation of Crimea, Reuters reported. Kerry said he said that if Russia holds the referendum, the U.S. and Europe will take a "serious series of steps" on Monday against Russia.
A state department official told the New York Times that Kerry said the referendum would "close any available space for diplomacy."
The U.S. response to Russia would likely include sanctions.
According to Reuters, Kerry also said that Russia doesn't have resources necessary to take over all of Ukraine. Kerry said that he believed there are over Russian 20,000 troops in Crimea.
The U.S. has been trying to get Russia to agree to hold formal talks on the situation, but Russia has stood their ground. German Prime Minister Angela Merkel warned of "massive" consequences if Russia continues to attempt an annexation in Crimea.
Kerry said he hoped Russia would agree to negotiations. From Reuters:
Kerry told a congressional hearing he hoped to avoid such steps, which include sanctions, through discussions with his Russian counterpart, Sergei Lavrov, in London on Friday.
"If there is no sign of any capacity to be able to move forward and resolve this issue there will be a very serious series of steps in Europe and here with respect to the options that are available to us," Kerry said in testimony on the State Department's 2015 budget request.
Putin has repeatedly insisted that Russia's actions in the Ukraine are legal.
Russia announced on Thursday that it would be massing troops near the Ukraine border for military exercises.