The State Department on Wednesday accused Russian President Vladimir Putin of lying about the crisis in Ukraine, releasing a list of 10 recent claims by the Russian president they argue are false.
"The world has not seen such startling Russian fiction since Dostoyevsky wrote, 'The formula 'two plus two equals five' is not without its attractions,' " the department said in the release.
"While these units wear uniforms without insignia, they drive vehicles with Russian military license plates and freely identify themselves as Russian security forces when asked by the international media and the Ukrainian military," the State Department said. "Moreover, these individuals are armed with weapons not generally available to civilians."
The Obama Administration also accused Putin of violating a 1997 Friendship Treaty, falsely declaring a humanitarian crisis and saying that ethnic Russians and Russian bases were under threat.
"Outside of Russian press and Russian state television, there are no credible reports of any ethnic Russians being under threat," the State Department said. "The new Ukrainian government placed a priority on peace and reconciliation from the outset."
The more aggressive rhetoric from the State Department comes as President Obama is looking to ratchet up pressure on Putin to withdraw his troops from Crimea.
Secretary of State John Kerry has threatened economic sanctions if Russians continue their military presence, and the White House said Obama and British Prime Minister David Cameron discussed their "grave concern" with developments in a phone call earlier Wednesday.
"The leaders expressed their grave concern over Russia’s clear violation of Ukrainian sovereignty and territorial integrity, and both noted that the current circumstances are unacceptable," the White House said in a statement. "Russia has already started to pay a cost for its actions, such as reducing investor confidence in Russia."
The call was Obama's second with a major European ally in less than 24 hours. On Tuesday, he spoke with German chancellor Angela Merkel for an hour about developments in the former Soviet republic.
According to the White House, the pair discussed ways to calm the crisis, sparked by Russia’s move over the weekend into the Crimean Peninsula, an ethnically Russian region just across the border.
A senior administration official told CNN that Merkel was looking for a way to construct a so-called “off ramp” that would enable Russian President Vladimir Putin to navigate out of the rapidly developing crisis.
Under the proposal, the international community would deploy observers to ensure the rights of ethnic Russians in Ukraine. Putin has suggested that those Russian nationals are under threat from the new Ukrainian government, a charge leaders there and in the U.S. have denied.