The United States has warned Russia that any moves to annex Crimea would close the door to diplomacy. In a telephone conversation, the American Secretary of State John Kerry has told his Russian counterpart Sergei Lavrov that __________________________ President Obama has been discussing the deepening crisis with world leaders. More than 50 international observers from the Organization for Security and Cooperation in Europe have been turned back as they tried to enter Crimea, as in previous occasions, they were stopped by pro-Russia paramilitaries. Ben Brown is in Sevastopol. 美国警告俄罗斯,任何企图吞并克里米亚的行为都将导致美俄外交关系中断.美国国务卿约翰?克里在与俄罗斯外长谢尔盖?拉夫罗夫通电话时表示,___________________________________美国总统奥巴马与世界其他国家领导人就不断深化的危机进行商议.欧洲安全与合作组织的50多名国际观察员试图进入克里米亚,但和前几次一样遭到支持俄罗斯的准军事部队拦截,只能无功而返.本?布朗从塞瓦斯托波尔发回的报道.