Russia is closely monitoring the situation following a subcritical nuclear test conducted at an underground nuclear site in the US state of Nevada last week, Deputy Foreign Minister Sergei Ryabkov said on Monday.
"We are closely monitoring what is happening at the American nuclear testing site. Of course, we took note of all public messages that the US administration has released in this regard," Ryabkov told reporters.
The diplomat stressed that as long as the Unites States conducted no full-scale nuclear tests, either would Russia.
"But we have also taken note of signals that they are considering further developing [the nuclear arsenal], including both delivery vehicles and warheads. It is a serious development that we will factor in our planning," Ryabkov said.
Washigton argued that the test was consistent with the moratorium on nuclear explosive testing that the United States implemented in 1992 because the test did not involve a self-sustaining, supercritical chain reaction.