President Trump's ultimatum to Russia over a landmark arms control treaty could potentially kill the pact and set the stage for more land-based cruise missiles and nuclear warheads in Europe, experts and Democrat lawmakers warn.

The Trump administration on Tuesday said it would suspend its obligations under the Intermediate-Range Nuclear Forces (INF) Treaty in 60 days if Russia did not get back in line with the pact. The decades-old nuclear arms agreement has kept Russia and the U.S. from developing and testing certain intermediate-range missiles.

Russia denies it is in violation of the treaty. And with chances slim that Moscow will meet U.S. the demands, some experts are sounding the alarm.

“We’re going to increase the risk that a crisis could go nuclear,” said Jon Wolfsthal, the National Security Council senior director for arms control and nonproliferation under former President Obama.

“It’s almost certain the Trump administration will pull out of the treaty,” added Wolfsthal, now senior advisor to Global Zero USA, an international nuclear-reduction initiative.

Secretary of State Mike Pompeo announced the INF suspension on Tuesday following meetings with NATO foreign ministers, describing Russia’s violations of the INF as part of a broader pattern of “lawlessness” by Moscow on the global stage. 

The move was expected. President Trump signaled in October that he planned to unilaterally withdraw the United States from the pact.

NATO ministers also released a statement agreeing unanimously that Moscow was in violation of the treaty.

“Allies have concluded that Russia has developed and fielded a missile system, the 9M729, which violates the INF Treaty and poses significant risks to Euro-Atlantic security. We strongly support the finding of the United States that Russia is in material breach of its obligations under the INF Treaty,” the NATO foreign ministers said in a statement. 

Experts as well as current and former officials mostly agree that Moscow is in violation of the accord – which bans all land-based cruise missiles with a range between 500 and 5,500 kilometers. But some worry the decision to withdraw from the treaty could spur an arms race.

In response to the ultimatum, Putin warned that Russia would begin to develop the disputed nuclear weapons if the U.S. withdraw.

An end to INF would allow Russia to keep the missiles it has been building and deploying, while the United States – possessing no similar missile that could be deployed in Europe – would be “letting the Russians off almost Scott free,” Wolfsthal said.

“In the long run, as we develop more missiles, as we either deploy them in Asia or as we try to respond to Russian deployments," he said. "We’re going to add new rungs on the nuclear ladder of escalation.”

Some U.S. lawmakers have criticized Trump for not properly consulting Congress or NATO in the decision.

“The Trump administration is unilaterally taking action on the INF Treaty without meaningful consultation and coordination with our NATO allies,” Rep. Adam Smith (D-Wash.), who will be the House Armed Services Chairman in the next Congress, said in a statement.

Smith also took aim at national security adviser John Bolton, who has long opposed the treaty.

“It is no secret that some of President Trump’s advisers are more focused on promoting U.S. withdrawal from its international commitments than prioritizing the collective security of America and its partners and allies,” he said.

Republican lawmakers, meanwhile, have lauded the administration’s decision as a necessary step to reign in “Russian deception,” according to Senate Armed Services Committee Chairman Jim Inhofe (R-Okla.).

“For too long, Vladimir Putin has openly flaunted the INF treaty and President Trump is right to put him on notice. The United States will no longer tolerate Russian deception at the expense of national security and the security of our allies,” Inhofe said in a statement.

“A treaty with only one side complying is unsustainable. Can Putin be trusted to uphold Russia’s international commitments? I won’t hold my breath.”  

Sens. Tom Cotton (R-Ark.), meanwhile, asserted that Washington needs to “change old policies to ward off new threats” and “must not allow our authoritarian rivals to build and deploy dangerous, destabilizing weapons while we keep one hand tied behind our back.” 

Wolfsthal though worried that the administration has provided no way to ease tensions. He criticized Trump officials for not giving the Russians any sort of off-ramp.

“Nobody really thinks that the Russians, even it good times, are going to back down, but not giving them a face-saving way out really seals the fate of the treaty,” Wolfsthal said.

Conservative experts have taken a different view.

James Carafano, a defense policy expert at the Heritage Foundation agreed that the “chances of Russians coming back into compliance in the next 60 days are likely zero.” But he called the pressure simply “the first step in a series of chess moves” by the United States.

“I don’t think the risks are very high,” he said of Trump abandoning the treaty.

Should the administration decide to withdraw from the agreement, language of the treaty stipulates that the six-month notice period to officially exit the pact.

Both sides acknowledge the high-stakes involved in Trump's gambit.

“I think the gains are we have put additional strategic pressure on the Russians, that this is now something that they have to take into account. It has, I think, enhanced the U.S. negotiating position,” Carafano added. "It definitely has helped strengthen broad European resolve that Russia is a destabilizing and threatening force."

Wolfsthal though sees Trump looking to walk from the pact.

“The Trump administration really doesn’t want a deal, " he said. "They want to get out.”