WASHINGTON (AP) — Eyeing each other warily across negotiating tables, U.S. and Russian diplomats never much trusted each other. Yet even during the Cold War, they hashed out agreements on the biggest issues of the day.

Now the fierce, mutual hostility over Russia’s invasion of Ukraine raises a critical question: Is U.S.-Russian diplomacy effectively dead?

The answer is crucial for reasons that go far beyond the Ukraine war and the immediate interests of both nations.

The United States and Russia have been at the center of almost every item on the global agenda, including arms control, space cooperation, cybersecurity and climate change. Progress on those issues and more, such as Arctic policy and maritime and aviation safety, largely depend on the two giants finding common ground.

There hasn’t been a total breakdown in diplomatic ties. For the moment at least, embassies remain open in both capitals despite a festering but unrelated diplomatic spat that has seen the two sides expel dozens of diplomats since 2017. And both Russia and the United States are involved in negotiations about reviving the 2015 Iran nuclear deal, now underway in Vienna.

The “hotline” — communication channels aimed at preventing a nuclear conflict — remains in place.

But aside from the Vienna talks, the most recent significant communication between the two sides appears to have been the U.S. notification to Russia on Monday that it would expel 12 Russians from the United Nations on espionage grounds.

Secretary of State Antony Blinken, whose spokesman last week accused the Russians of engaging in diplomatic “kabuki theater,” said the door to diplomacy remains open but only narrowly and only if Moscow halts its military offensive.

“What we’ve seen repeatedly is that Russia goes through the pretense of diplomacy to distract and continue on its aggressive path,” Blinken told reporters Wednesday.

“If we determine that there are areas that it’s in our interest to continue to pursue that may involve some engagement for Russia, we’ll continue to pursue that,” he said, adding however that “we’re not going to let Russia dictate in any way what’s in our interests and how to pursue it.”

At the highest level, President Joe Biden and Russian leader Vladimir Putin have not spoken since a roughly hourlong phone call on Feb. 12, in which Biden told Putin that a “Russian invasion of Ukraine would produce widespread human suffering and diminish Russia’s standing.” Twelve days later, Russia invaded.

The last contact between the nations’ top diplomats — Blinken and Russian Foreign Minister Sergey Lavrov — occurred on the eve of the invasion. On Feb. 23, Blinken wrote to Lavrov to say he was canceling a scheduled meeting in Geneva the next day because he did not believe it would be productive. Lavrov replied with a cursory note blaming any lack of productiveness on inflexible American positions, according to U.S. officials.

Other than that, the last publicly acknowledged contact may have been the U.S. informing Russia on Feb. 23 that it was expelling the No. 2 at its embassy in Washington in retaliation for Russia’s expulsion of the U.S. deputy ambassador from Moscow in mid-February.

The dearth of contact, apart from angry statements delivered by both sides at the United Nations, is problematic.

“Generally one should preserve the ability to talk, and at the end of the day one usually finds ways to do what needs to be done,” said Ronald Neumann, the president of the American Academy of Diplomacy and a former three-time U.S. ambassador. “Russia won’t be isolated forever, but right now there is a need to send them a message. We can’t wink at them extinguishing a sovereign country.”

Neumann noted that even during the Cuban missile crisis in the 1960s there were secret contacts, often involving intermediaries, despite bluster from both Washington and Moscow, and eventually there was a peaceful resolution. Cooler heads, he said, should prevail eventually as the impact of the lack of diplomacy becomes clearer.

“We, too, will pay a price for isolating Russia,” he said. “But right now that appears to be a price that we should pay (because) we don’t want to give the Russians a free hand.”

With a wide-ranging list of potential areas of cooperation, the Biden administration has sought to ensure that not all contacts are banned. It has barred most U.S. diplomats from formal interactions with their Russian counterparts overseas, but the State Department said Tuesday that U.S. Ambassador to Russia John Sullivan has been in touch with counterparts in Moscow in recent days.

The exemptions to barred contacts include not just the Iran talks but discussions with Russia at most international forums like the United Nations. They also include direct talks with Moscow on consular issues, which for the United States means primarily the fate of at least two Americans detained on what Washington says are specious espionage charges.

For Russia, though, the appearance of diplomacy remains. Even as Russian troops have pressed their offensive deeper into Ukraine amid international outrage and increasing international isolation, Lavrov has sought to continue business as usual, talking about arms control in remarks to a U.N. disarmament conference in Geneva on Tuesday.

He spoke via video link after several EU nations barred him from flying there because of a European ban on Russian planes, part of bruising sanctions against Moscow. Lavrov berated the EU members for their “refusal to respect the right to freedom of movement, which is a fundamental human right.”

After repeating a litany of accusations against Ukraine and the West for moves he said were threatening Russia’s security, Lavrov spoke about Moscow’s readiness to continue the talks on arms control and European security — a statement that rang hollow as the war in Ukraine made such negotiations irrelevant.

He denounced what he called NATO’s policy to contain Russia and its refusal to meet Moscow’s demand to keep Ukraine out of NATO and roll back alliance military deployments in Eastern Europe.

“I am once again urging the United States, its allies and clients to unfailingly honor their obligations not to strengthen their own security at the expense of others,” Lavrov said. “Obviously, this would help improve the military-political situation in the Euro-Atlantic region and create prerequisites for making headway on the entire range of matters in the field of arms control, including possible work on new agreements.”