Following the White House's strong condemnation of violence by Ukraine's security forces, US Vice President Joe Biden demanded that President Viktor Yanukovych immediately take "tangible steps to work with the opposition on a path forward that addresses the legitimate aspirations of the Ukrainian people." During a phone call between the two leaders, late on Thursday, Biden urged Yanukovych to "pull back all security forces - police, snipers, military and paramilitary units, and irregular forces," and "made clear that the United States is prepared to sanction those officials responsible for the violence." He further stressed that the US "supports an independent, democratic Ukraine that pursues the future its people choose," something he also discussed on a call with Polish Prime Minister Donald Tusk, as they "discussed steps the United States, Poland, and the European Union are taking to support an end to the violence and a political solution that is in the best interests of the Ukrainian people." Meanwhile, the Obama administration's most senior diplomat expressed deep frustration at the retaliation witnessed around the world against Kyiv's demonstrators, insisting "the people of Ukraine deserve far better than senseless death and suffering on the streets of one of Europe's great cities." In a statement also released late Thursday, Secretary of State John Kerry conveyed feelings of "anger" and "anguish" at the renewed violent struggle on the streets, only hours after the government announced a truce with the protesters. "The violence must stop," said Kerry. "The people of Ukraine and the international community will hold to account those who are responsible for what has occurred, and the United States has already begun implementing sanctions through travel bans on Ukrainians responsible for the violence." "Protestors should exercise their rights peacefully, and we urge the Ukrainian military to remain true to its non-political heritage and its professional traditions," he added. Describing them as "difficult days," Kerry also called for assistance from the international community to help the divided country "return to stability," and reaffirmed U.S. support for its citizens. "There is no time for brinksmanship or gamesmanship. President Yanukovich must undertake serious negotiations with opposition leaders immediately to establish a new interim government that will have broad support," he stressed. "That is the only way to begin the difficult but essential constitutional and economic reforms that Ukraine needs." Seventy-five people have died in Kyiv - most having been killed in the last 48 hours - in what is being heralded as the worst violence in the country since the Soviet era, which ended 22 years ago. The European Union, which was first to declare sanctions on Thursday, has sent ministers to try and broker a political deal.