Kiev, Ukraine (CNN) -- [Breaking news alert, 1:37 p.m. ET]
-- U.S. Secretary of State John Kerry told reporters Thursday that he spoke with Russian Foreign Minister Sergey Lavrov, and the two have agreed to continue talking "over the course of the next hours, the next days'' to try to find a political solution to end the crisis in Ukraine.
"As you have heard me say all week, the choices that Russia has made escalated this situation, and we believe Russia has the opportunity now ... to de-escalate," he said.
-- President Barack Obama said on Thursday that a proposed referendum for Crimea to join Russia would violate the Ukrainian constitution and international law.
"Any discussion about the future of Ukraine must include ... the government of Ukraine," he said.
[Breaking news alert, 1:14 p.m. ET]
