<span style="color: #222222;">The United States has warned Russia of catastrophic consequences if it uses nuclear weapons against Ukraine. Yesterday, US Secretary of State Antony Blinken said, it is very important that Russia hear from the world and that the consequences would be horrific. <br />''<br />''Earlier, President Vladimir Putin warned that he would use any means to defend Russia. On other hand, voting is set to close today of referendums organized by Russia-backed authorities in four parts of Ukraine. However, the Ukrainian government and its western allies reject the polls, calling them a sham.</span><br />