Moscow on Sunday warned US President Donald Trump that his plan to ditch a Cold War-era nuclear weapons treaty with Russia was a dangerous step.
He insisted that Moscow observed "in the strictest way" the three-decade-old Intermediate-Range Nuclear Forces Treaty, known as the INF, while accusing Washington of "flagrant violations."
The treaty was signed in 1987 by the then US president Ronald Reagan and Soviet leader Mikhail Gorbachev.
But Trump on Saturday claimed Russia had long violated it.
"We're the ones who have stayed in the agreement and we've honored the agreement, but Russia has not unfortunately honored the agreement, so we're going to terminate the agreement and we're going to pull out," he told reporters.
"Russia has violated the agreement. They've been violating it for many years. I don't know why president (Barack) Obama didn't negotiate or pull out. And we're not going to let them violate a nuclear agreement and go out and do weapons (while) we're not allowed to."
Trump's National Security Advisor John Bolton was set to arrive in Moscow on Sunday evening and meet next week with Russia's Foreign Minister Sergei Lavrov.
That comes ahead of what is expected to be a second summit between Trump and Russian leader Vladimir Putin this year.
Bolton was also set to meet with Security Council Secretary Nikolai Patrushev and Putin aide Yuri Ushakov. Kremlin spokesman Dmitry Peskov said a "possible meeting" was being prepared between Putin and Bolton.
Deputy foreign minister Ryabkov said Sunday he hoped Bolton would explain the US plans "more substantively and clearly."
The Trump administration has complained of Moscow's deployment of 9M729 missiles, which Washington says can travel more than 310 miles (500 kilometres), and thus violate the INF treaty.
The treaty, which banned missiles that could travel between 310 and 3,400 miles, resolved a crisis that had begun in the 1980s with the deployment of Soviet SS-20 nuclear-tipped, intermediate-range ballistic missiles targeting Western capitals.