By ERIN BANCO and PAUL MCLEARY

Some countries with populations that support Russia are blaming Washington for rising energy costs.

The concerns have sparked a flurry of calls among top U.S. officials across the administration about how to keep European leaders aligned with the American strategy, two senior U.S. officials said. Washington increasingly believes that a consistent and unified messaging campaign with Europe is critical to success in Ukraine, and that any fracturing of support for Kyiv could give Russia leverage both on and off the battlefield.

Growing economic concerns have led to protests in some European cities over rising inflation and the high cost of heating as temperatures drop, putting more pressure on governments to weigh domestic issues against support for Ukraine.

“The one thing that I do worry about is a rift between the United States and Europe because the United States looks better positioned on energy because we’re a major producer,” said Fiona Hill, former Russia director of the National Security Council. “We should have been working on this transition earlier.”

One of the U.S. officials said “things are holding steady for now,” adding: “but it is a shaky situation.” The official, like others quoted for this story, was granted anonymity to discuss internal deliberations.

The State Department declined to comment.

The Kremlin’s decision to halt energy shipments due to sanctions has caused many European capitals to shift their attention from supporting Ukraine’s military “to dealing with the energy crisis,” said Max Bergmann, European program director at the Center for Strategic and International Studies.

European Union countries are “really struggling with how to handle the energy crisis and are throwing Covid-style relief packages together to get the public through the winter,” he said.

Some officials, though, are confident that support from Europe and other allies will last.

“When it comes to the decisions of the governments, I see unwavering support” for Ukraine, a NATO official told reporters this week.

The warnings about maintaining Europe’s support are heightened by U.S. officials’ concerns about Russia’s nuclear threat in Ukraine.

American officials believe Russia could rely on its nuclear deterrence forces as the country’s troops continue to lose ground in Ukraine, according to U.S. intelligence reports circulated inside the administration over the past month. The intelligence did not warn of any imminent nuclear threat.

While some officials are actively worried about the threat, others inside the Biden administration are downplaying the situation, assessing that Russia wants to avoid a confrontation in Ukraine and that Russian President Vladimir Putin is using the threat as a negotiating tactic to pressure Ukraine to make concessions on the battlefield, the two officials said.

“This is Putin engaging in nuclear blackmail,” Hill said. Putin “is thinking about how he can do it. Therefore we have to act to make it impossible, or to make it very clear, that he won’t get the desired effect from it. That’s why we have to be really serious about the diplomacy. We have to frame it with other nuclear powers to say ‘this is impermissible.’”

In response to the nuclear concerns, U.S. national security officials and diplomats are ratcheting up their communication with counterparts in allied countries to clarify Washington’s strategy in Ukraine and solidify European support through the winter.

In recent meetings with top European officials in Brussels, London and Berlin, the U.S. pushed the message that sanctions are strangling Russia’s economy.

Meanwhile, officials at the Pentagon are solidifying support from NATO allies on continuing to boost Ukraine militarily. During a closed-door meeting with NATO leaders in Brussels in October, Defense Secretary Lloyd Austin stressed the need to continue to support Ukraine by transferring more weapons, including equipment that can work with NATO gear. Austin acknowledged Ukraine’s desire to join NATO, but said he did not see any decisions being made in the short term. Other NATO representatives, including those from Poland and Greece, said they supported Ukraine’s bid, according to one of the officials and a readout of the meeting obtained by POLITICO.

U.S. officials said they are hopeful their recent outreach will ease tensions with other European countries.

Officials have also spoken with their European counterparts about the importance of continuing to participate in talks with Russia over the next several months.

U.S. officials across the Biden administration have for weeks engaged with their Russian counterparts both directly and indirectly through intermediaries, the two officials said, declining to comment on the contents of those talks. One of the officials described the communications as “normal and routine.” The other said the two sides have discussed “a range of issues.”

The Biden administration told lawmakers this fall — before the publishing of a Congressional Progressive Caucus letter calling for the U.S. to engage diplomatically with Russia — that senior diplomats and national security officials were actively engaged in talks with Russia on a variety of matters, a person with direct knowledge of the conversations said.

National Security Council spokesperson Adrienne Watson would not comment on the specifics of U.S. communications with Russia, but said the administration has “the capacity to speak directly at senior levels with the Russian government when necessary.”

“That has happened over the past several months,” she said. “The sole purpose of this is to discuss risk reduction in the U.S.-Russia relationship. It has nothing to do with diplomacy or anything else about Ukraine.”

The NATO official who spoke to reporters this week said Russia’s nuclear rhetoric has cooled in recent days, and “we don’t see any preparations in practical terms on the Russian side with regard to their nuclear arsenal.” The official added that “a nuclear war shouldn’t be fought and can never be won, and I think we are in the situation where the Russians actually think the same.”

Hill said any conversations about Russia’s nuclear threat “cannot be done bilaterally between the U.S. and Russia.”

“He’s not threatening us with a nuclear weapon. He’s threatening Ukraine with a nuclear weapon,” she said.

U.S. officials have said that any talks with Russia about a potential settlement need to be agreed to and supported by Ukraine. In an address Monday, Ukrainian President Volodymyr Zelenskyy said he was open to “genuine” peace talks with Russia, but that his most immediate concern was putting a stop to recent Russian aggression, including a barrage of attacks on critical infrastructure.

State Department spokesperson Ned Price told reporters Tuesday that the U.S. and Russia are set to resume formal talks on nuclear inspections under the terms of the New Strategic Arms Reduction Treaty.

“We believe deeply … in the transformative power and the importance of diplomacy and dialogue,” Price said. “When it comes to Russia, we are clear-eyed and realistic about what dialogue between the United States and Russia — what it can entail and what it can accomplish.”

One person familiar with the plans to talk with the Russians said the U.S. approach will remain narrowly focused on the New START issue, as officials are wary of wandering off topic at such a tense moment.