Moscow( CNN) Russia to understand why the United States wants to withdraw from a 30 -year-old nuclear non-proliferation treaty, US National Security Adviser John Bolton told CNN.

“I think their preference is that they have stayed in this and we do not withdraw, but we are giving them the reasons why we are going do it.”

Bolton spoke to reporters in Moscow on Tuesday morning after laying blooms at the place where Russian opposition leader Boris Nemtsov was killed.