Nuclear experts and peace advocates on Friday shared their heightened concerns about a new arms race as the Trump administration officially withdrew from a landmark treaty with Russia that was signed by former U.S. President Ronald Reagan and Soviet leader Mikhail Gorbachev in 1987.

"By walking away from the INF Treaty, Donald Trump and Vladimir Putin have further undermined the Non-Proliferation Treaty (NPT) and put the world at heightened risk of nuclear weapons use and war."

—ICANDespite warnings about how ditching the Intermediate-Range Nuclear Forces (INF) Treaty could impact global security, U.S. President Donald Trump suspended U.S. obligations under the decades-old deal in February, notifying Moscow that it had six months to destroy weapons that Washington and NATO claim violate the agreement.

Russian President Vladimir Putin quickly followed suit, suspending his country's commitments under the Cold War-era treaty, which banned either party from possessing nuclear and non-nuclear missiles with ranges between 310 and 3,400 miles, excluding those launched from sea.

U.S. Secretary of State Mike Pompeo confirmed in a statement Friday that the United States has withdrawn from the deal "because Russia failed to return to full and verified compliance through the destruction of its non-compliant missile system—the SSC-8 or 9M729 ground-launched, intermediate-range cruise missile."

Pompeo declared Russia "solely responsible for the treaty's demise" and noted that Washington first raised concerns with Moscow about the weapon in question in 2013, under the Obama administration. As Pompeo put it, "Russia subsequently and systematically rebuffed six years of U.S. efforts seeking Russia's return to compliance."

Moscow maintains its cruise missiles do not violate the treaty but that the U.S. missile defense systems in Europe do—a charge that Washington has denied. In a statement to Russian state-run Ria Novosti news agency reported by BBC News Friday, Russia's foreign ministry confirmed that the treaty was "formally dead."

"The risk of nuclear weapons use is already unacceptably and unnecessarily high. The death of the INF Treaty, without any plan in evidence to compensate for the deterioration of arms control, will only accelerate our downward spiral into nuclear chaos and potential catastrophe," warned Jon Wolfsthal, director of the Nuclear Crisis Group, an international task force of top former nuclear commanders, senior military officials, and diplomats that came out of the disarmament campaign Global Zero.

The International Campaign to Abolish Nuclear Weapons (ICAN) said in a statement (pdf) that it "deplores the irresponsible destruction" of the agreement and "by walking away from the INF Treaty, Donald Trump and Vladimir Putin have further undermined the Non-Proliferation Treaty (NPT) and put the world at heightened risk of nuclear weapons use and war."

ICAN—which was awarded the 2017 Nobel Peace Prize for its work to advance nuclear disarmament—urged the United States and Russia to pursue urgent talks to restore compliance and fully implement the INF Treaty, scale back their respective nuclear arsenals, and "pave the way for nuclear-free security by joining the U.N.'s multilateral Treaty on the Prohibition of Nuclear Weapons (TPNW), which was negotiated and adopted by over 122 nations at the U.N. General Assembly in 2017."

The #INF Treaty between the US & Russia expires today- putting the entire world at risk of a new nuclear arms race & relapse into Cold War-II. Here are 9 things you need to know about it https://t.co/l4adf5g6Ic #thread pic.twitter.com/b6EzqSwyaG — ICAN (@nuclearban) August 2, 2019 That’s where the #nuclearban treaty comes in- in 2017 the international community decided to put an end to nuclear weapons & now it’s time for all world leaders to step up and sign the nuclear ban treaty. It’s time to end nuclear weapons for good. — ICAN (@nuclearban) August 2, 2019

John Woodworth, a former U.S. ambassador and deputy negotiator for the INF Treaty, wrote in an analysis for the Bulletin of the Atomic Scientists Friday that "the central lesson of the INF negotiations was that an agreement as significant as the INF Treaty is not possible without strong political leadership."

"It might have been possible to salvage the treaty if political will had existed to hammer out solutions to outstanding issues," Woodworth continued. "Instead, we are at the cusp of a new arms race in Europe and Asia. Perhaps it was only a moment in time, but the INF Treaty pointed toward what can be done to achieve a safer and more secure world. It would be regrettable to lose sight of these ambitions."

Physicist David Wright, co-director of the Global Security Program at the Union of Concerned Scientists (UCS), said in a statement Friday that "withdrawing from this landmark treaty is shortsighted and will ultimately undermine the security of the United States and its allies. The president's decision will increase tensions between the United States and Russia and open the door to a competition in conventionally armed missiles that will undermine stability."

"To claim the United States is justified in pulling out of the treaty because of Russian violations does not take the full picture into account," Wright added. "What apparently underlies this decision is the administration's aversion to negotiated agreements that in any way constrain U.S. weapons systems."

Outlining what a world without the treaty could look like, The Associated Press reported Friday:

Washington has complained for years that the arms control playing field was unfair. U.S. officials argued that not only was Russia violating the treaty and developing prohibited weapons, but that China also was making similar non-compliant weapons, leaving the U.S. alone in complying with the aging arms control pact. Now, the U.S. is free to develop weapons systems that were previously banned. The U.S. is planning a test flight of such a weapon in coming weeks, according to a senior administration official, who was not authorized to publicly discuss the weapons development and spoke only on condition of anonymity.

Both UCS's Wright and the Nuclear Crisis Group's Wolfsthal expressed concern about the future of the last remaining nuclear control agreement with Russia: the New Strategic Arms Reduction Treaty (START). Under that agreement—which expires on Feb. 5, 2021 unless it is extended by Trump and Putin—the U.S. and Russia can only have 1,550 strategic nuclear weapons each.

"If President Trump pulls out of that treaty as well or allows it to lapse, it will be the first time since 1972 that the two countries will be operating without any mutual constraints on their nuclear forces," Wright pointed out.

"Russia remains in full compliance, and the U.S. military and intelligence communities fully support extending the agreement," Wolfsthal explained. "Regardless, it now looks like Trump and [National Security Adviser John] Bolton are prepared to either let the deal expire, or to move to terminate it before the end of Trump's first term. Congress must make sure this does not happen, and the international community, especially U.S. allies who understand New START is essential to their own security, must also start to make their voices more clearly heard."