MOSCOW (AP) — Russia raised the stakes Thursday in its dispute with the West over Ukraine and the North Atlantic Treaty Organization’s (NATO) expansion when a top diplomat refused to rule out a military deployment to Cuba and Venezuela if tensions with the United States escalate.

Deputy Foreign Minister Sergei Ryabkov said he could “neither confirm nor exclude” the possibility of Russia sending military assets to Latin America if the U.S. and its allies don’t curtail their military activities on Russia’s doorstep.

“It all depends on the action by our U.S. counterparts,” the minister said in an interview with Russian television network RTVI, citing Russian President Vladimir Putin’s warning that Moscow could take unspecified “military-technical measures” if the U.S. and its allies fail to heed its demands.

Ryabkov led a Russian delegation in talks with the U.S. on Monday. The negotiations in Geneva and a related NATO-Russia meeting in Brussels took place in response to a significant Russian troop buildup near Ukraine that the West fears might be a prelude to an invasion.

Russia, which annexed Ukraine’s Crimea Peninsula in 2014, has denied having plans to attack the neighboring country. The Kremlin reacted to the suggestion by accusing NATO of threatening its territory and demanding that the military alliance never embrace Ukraine or any other ex-Soviet nations as new members.

Washington and its allies firmly rejected the demand this week as a nonstarter, but the NATO and Russian delegations agreed to leave the door open to further talks on arms control and other issues intended to reduce the potential for hostilities.

A senior Biden administration official suggested Thursday that Ryabkov’s statement about Cuba and Venezuela had not changed Washington’s calculations.

“We are not going to respond to bluster. If Russia actually started moving in that direction, we would deal with it decisively,” said the official, speaking on condition of anonymity to discuss the ongoing negotiations.

Ryabkov last month compared the current tensions over Ukraine with the 1962 Cuban Missile Crisis — when the Soviet Union deployed missiles to Cuba and the U.S. imposed a naval blockade of the island.

That crisis ended after U.S. President John F. Kennedy and Soviet leader Nikita Khrushchev agreed that Moscow would withdraw its missiles in exchange for Washington’s pledge not to invade Cuba and the removal of U.S. missiles from Turkey.

Putin, in seeking to curtail the West’s military activity in Eastern Europe, has argued that NATO could use Ukrainian territory to deploy missiles capable of reaching Moscow in just five minutes. He warned that Russia could gain a similar capability by deploying warships armed with the latest Zircon hypersonic cruise missile in neutral waters.

Soon after his first election in 2000, Putin ordered the closure of a Soviet-built military surveillance facility in Cuba as he sought to improve ties with Washington. Moscow has intensified contacts with Cuba in recent years as tensions with the U.S. and its allies mounted.

In December 2018, Russia briefly dispatched a pair of its nuclear-capable Tu-160 bombers to Venezuela in a show of support for Venezuelan President Nicolas Maduro amid Western pressure.

Ryabkov said a refusal by the U.S. and its allies to consider the key Russian demand for guarantees against the alliance’s expansion to Ukraine and other ex-Soviet nations makes it hard to discuss the confidence-building steps that Washington says it’s ready to negotiate.

“The U.S. wants to conduct a dialogue on some elements of the security situation … to ease the tensions and then continue the process of geopolitical and military development of the new territories, coming closer to Moscow,” he said. “We have nowhere to retreat.”

Ryabkov described U.S. and NATO military deployments and drills near Russia’s territory as extremely destabilizing. He said U.S. nuclear-capable strategic bombers flew just 15 kilometers (9 miles) from Russia’s border.

“We are constantly facing a provocative military pressure intended to test our strength,” he said, adding that he wondered how Americans would react “if our bombers fly within 15 kilometers off some U.S. bases on the East or the West Coast.”

The high-stakes diplomacy this week took place as an estimated 100,000 Russian troops with tanks and other heavy weapons are massed near Ukraine’s eastern border. Kremlin spokesman Dmitry Peskov on Thursday rebuffed the West’s calls for a troop pullback from areas near Ukraine.

“It’s hardly possible for NATO to dictate to us where we should move our armed forces on Russian territory,” he said.

Peskov said this week’s talks produced “some positive elements and nuances,” but he characterized them as unsuccessful overall.

“The talks were initiated to receive specific answers to concrete principal issues that were raised, and disagreements remained on those principal issues, which is bad,” Peskov said in a conference call with reporters.

He warned of a complete rupture in U.S.-Russia relations if proposed sanctions targeting Putin and other top civilian and military leaders are adopted. The measures, proposed by Senate Democrats, would also target leading leading Russian financial institutions if Moscow sends troops into Ukraine.

Russian Foreign Minister Sergey Lavrov likewise denounced the proposed sanctions as a reflection of U.S. “arrogance,” adding that Moscow expects a written response to its demands from the U.S. and NATO next week in order to mull further steps.

Tensions revolving around Ukraine and Russia’s demands on the West again appeared on the table at a Thursday meeting of the Organization for Security and Cooperation in Vienna.

Polish Foreign Minister Zbigniew Rau, who assumed the position of the OSCE’s chairman-in-office, noted in his opening speech that “the risk of war in the OSCE area is now greater than ever before in the last 30 years.”

The tensions over Ukraine also figured high on the agenda of a meeting of European Union foreign ministers in Brest, France. Danish Foreign Minister Jeppe Kofod said it’s important “for Putin to understand that the military threats, the game he’s playing, the way he’s trying to take us back to the darkest days of the Cold War, is totally unacceptable.”

The EU’s foreign policy chief, Josep Borrell, reiterated that “any further aggression against Ukraine will have massive consequences and severe costs for Russia.” Borrell said the 27-country bloc is providing 31 million euros (US$35.5 million) in logistical assistance to the Ukrainian army and is preparing to send a mission to help the country counter cyberattacks.

Russia seized the Crimean Peninsula after the ouster of Ukraine’s Moscow-friendly leader and in 2014 also threw its weight behind a separatist insurgency in eastern Ukraine. More than 14,000 people have been killed in nearly eight years of fighting between the Russia-backed rebels and Ukrainian forces.