The White House on Monday said it was "extremely concerned" by deteriorating conditions in southern Ukraine as officials in Kiev announced plans to mobilize troops to combat pro-Russian separatists threatening to seize control of the southern city of Odessa.
"We remain extremely concerned by the deteriorating situation in both eastern and southern Ukraine, where pro-Russian militants who are armed have escalated their already violent behavior and taken over additional government buildings in yet more towns," White House press secretary Jay Carney told reporters.
Carney added that the "violence and mayhem" in Odessa was "unacceptable" and said the battles "dramatically underscore the need for an immediate de-escalation of tensions in Ukraine."
"We're going to continue to call on Russia to live up to its commitments in Geneva and to use its influence over these groups, these pro-Russian militant groups, to urge them to disarm and to instead engage in Ukraine's political process," Carney said.
A fire at a government building in Odessa on Friday led to 46 deaths, and the White House called on Kiev to launch a full investigation.
But the White House did not indicate that its timeline for imposing additional sanctions might be dramatically hastened by the threat to Odessa. Were separatists to seize control of the vital port city, the government in Kiev would lose access to the Black Sea in a major blow for the fledgling interim government.
"We have, from day one, escalated our actions that impose costs on Russia, as Russia has escalated its interference in and efforts to destabilize Ukraine," Carney said. "And as the president made clear last week when we announced new sanctions, in coordination with our European and G-7 partners, those costs will continue to escalate."
Ukrainian Interior Minister Arsen Avakov said in a statement to The Associated Press that government troops were battling around 800 separatists using large-caliber weapons and mortars.