U.S. Vice President Joe Biden called Ukrainian President Viktor Yanukovych to express "grave concern" over the crisis on the streets of Kiev, the Office of the Vice President said Tuesday.The Office of the Vice President said in a statement that Biden called on Yanukovych "to pull back government forces and to exercise maximum restraint." "The Vice President made clear that the United States condemns violence by any side, but that the government bears special responsibility to de-escalate the situation," the statement stressed.Biden further underscored "the urgency of immediate dialogue with opposition leaders to address protesters' legitimate grievances and to put forward serious proposals for political reform." "The United States is committed to supporting efforts to promote a peaceful resolution to the crisis that reflects the will and aspirations of the Ukrainian people," the statement affirmed.