Time is running out: The nuclear arms reduction deal between the United States and Russia , known as New START, is set to expire by the end of Wednesday Eastern Standard Time (0500 Thursday UTC). Key world leaders, including Pope Leo XIV , have been publicly calling for the agreement's extension or preservation. START stands for Strategic Arms Reduction Treaty. The most recent bilateral deal between the US and Russia was signed by  Barack Obama and Dmitry Medvedev  as the respective presidents