Days after the U.S. ditched a Cold War-era weapons treaty with Russia, President Vladimir Putin on Monday said his country would move to develop new intermediate-range nuclear missiles if the U.S. did so first.

"If Russia obtains reliable information that the United States has finished developing these systems and started to produce them," Putin said in a statement, "Russia will have no option other than to engage in a full-scale effort to develop similar missiles."

The Russian leader blasted Washington's Friday exit from the Intermediate-Range Nuclear Forces Treaty, which was inked in 1987 by former President Ronald Reagan and former Soviet leader Mikhail Gorbachev. Putin said the move "seriously exacerbated the situation in the world and raised fundamental risks for all."

The INF Treaty, as Reuters reported "banned land-based missiles with a range of between 310 and 3,400 miles (500-5,500 km), reducing the ability of both countries to launch a nuclear strike on short notice." The U.S. accuses Russia of violating the agreement, while Russia has said the violations lie with Washington.

Given the new context, Putin said that to "avert chaos," the two nations should "start serious dialogue without any ambiguities."

A senior Russian official echoed that call.

"We are still open for an equal and meaningful dialogue with the United States on issues related to the INF Treaty and other strategic stability issues, based on mutual respect and mutual consideration of interests," said Russian Deputy Foreign Minister Sergei Ryabkov.

Pentagon chief Mark Esper signaled Friday that the U.S. may not be pursuing that avenue as a priority.

According to U.S. News,

In a statement Friday, the newly confirmed Esper said the Pentagon in 2017 began missile research and development within the parameters of the INF treaty in response to what he called "Russia's non-compliance." The activities centered on developing mobile, ground-based systems capable of launching cruise missiles and ballistic missiles. The military will step up that work now that it is unrestricted by the treaty, Esper said.[...] Though Esper specifically mentioned the technology under development is for conventional missiles, nuclear weapons analysts say the launchers could be used for other purposes. "It could emplace nuclear warheads on intermediate-range missiles, if it wanted to," says Alexandra Bell, senior policy director at the Center for Arms Control and Non-Proliferation.

Kate Hudson, general secretary of the U.K.-based Campaing for Nuclear Disarmament, said the recent developments were reason for worry.

"If we needed a clearer sign that this is now a nuclear arms race, Washington is set to trial new nuclear missiles that exceed the INF Treaty's limits and Moscow has similar plans," she said Friday. "It's a game of nuclear tit for tat in which there can be no winners as the threat of nuclear war rises."

In a tweet on Monday commenting on the end of the INF Treaty, the Center for Arms Control and Non-Proliferation warned that "a Pandora's Box of dangerous possibilities" was now open.