US Vice President Joe Biden arrived in Kiev Monday, the highest-ranking US official visitor since the start of the Ukraine crisis. He is to hold talks with the acting president and prime minister on the situation that remains tense despite the accord reached last week in Geneva. Biden’s spokesman said he had come to send a very clear message of “support for Ukraine's democracy, unity, sovereignty and territorial integrity” and added: …”there will be mounting costs for Russia if they choose a destabilizing rather than constructive course in the days ahead.”