The Biden administration and NATO told Russia on Wednesday there will be no U.S. or NATO concessions on Moscow’s main demands to resolve the crisis over Ukraine.

In separate written responses delivered to the Russians, the U.S. and NATO held firm to the alliance’s open-door policy for membership, rejected a demand to permanently ban Ukraine from joining, and said allied deployments of troops and military equipment in Eastern Europe are nonnegotiable.

“There is no change, there will be no change,” Secretary of State Antony Blinken said. Also not up for negotiation will be the U.S. and European response to any Russian invasion of Ukraine, he said, repeating the mantra that any such incursion would be met with massive consequences and severe economic costs.

The responses were not unexpected and mirrored what senior U.S. and NATO officials have been saying for weeks. Nonetheless, they and the eventual Russian reaction to them could determine whether Europe will again be plunged into war.

There was no immediate response from Russia but Russian officials have warned that Moscow would quickly take “retaliatory measures” if the U.S. and its allies reject its demands.

Read: Russia toughens its posture amid Ukraine tensions

Seeking possible off-ramps that would allow Russia to withdraw the estimated 100,000 troops it has deployed near Ukraine’s border without appearing to have lost a battle of wills, the U.S. response did outline areas in which some of Russia’s concerns might be addressed, provided it de-escalates tensions with Ukraine.

Speaking to reporters in Washington, Blinken said Russia would not be surprised by the contents of the several-page American document that U.S. Ambassador to Russia John Sullivan delivered Wednesday to the Russian Foreign Ministry.

“All told it sets out a serious diplomatic path forward. should Russia choose it,” he said. “The document we’ve delivered includes concerns of the United States and our allies and partners about Russia’s actions that undermine security, a principled and pragmatic evaluation of the concerns that Russia has raised, and our own proposals for areas where we may be able to find common ground.”

Blinken said he hoped to speak with Russian Foreign Minister Sergey Lavrov about the response in the coming days. But he stressed the decision about pursuing diplomacy or conflict rests with Russia and, more specifically, with Russian President Vladimir Putin.

“We’ll see how they respond,” he said. “But there’s no doubt in my mind that if Russia were to approach this seriously and in a spirit of reciprocity with a determination to enhance collective security for all of us, there are very positive things in this in this document that could be pursued. We can’t make that decision for President Putin.”

Shortly after Blinken spoke, NATO Secretary-General Jens Stoltenberg said in Brussels that the alliance had sent a separate reply to Russia with an offer to improve communications, examine ways to avoid military incidents or accidents, and discuss arms control. But, like Blinken, he rejected any attempt to halt membership.

“We cannot and will not compromise on the principles on which the security of our alliance, and security in Europe and North America rest,” Stoltenberg said. “This is about respecting nations and their right to choose their own path.”

“Russia should refrain from coercive force posturing, aggressive rhetoric and malign activities directed against allies and other nations. Russia should also withdraw its forces from Ukraine, Georgia and Moldova, where they are deployed without these countries’ consent,” he said.

While flatly refusing to consider any changes to NATO’s open-door policy, its relationship with non-ally Ukraine, or allied troop and military deployments in Eastern Europe, Blinken said the U.S. is open to other ideas to ease Russia’s stated concerns.

The U.S. proposals, echoed in the NATO document, include the potential for negotiations over offensive missile placements and military exercises in Eastern Europe as well as broad arms control agreements as long as Russia withdraws its troops from the Ukrainian border and agrees to halt inflammatory rhetoric designed to deepen divisions and discord among the allies and within Ukraine itself.

Moscow has demanded guarantees that NATO will never admit Ukraine and other ex-Soviet nations as members and that the alliance will roll back troop deployments in former Soviet bloc nations. Some of these, like the membership pledge, are nonstarters for the U.S. and its allies, creating a seemingly intractable stalemate that many fear can only end in a war.

The Kremlin has repeatedly denied it has plans to attack Ukraine, but the U.S. and NATO are worried about Russia massing its troops near Ukraine and conducting a series of sweeping military maneuvers.

As part of the drills, motorized infantry and artillery units in southwestern Russia practiced firing live ammunition, warplanes in Kaliningrad on the Baltic Sea performed bombing runs, dozens of warships sailed for training exercises in the Black Sea and the Arctic, and Russian fighter jets and paratroopers arrived in Belarus for joint war games.

Speaking to Russian lawmakers Wednesday before the U.S. and NATO responses were delivered, Lavrov said he and other top officials will advise Putin on the next steps.

“If the West continues its aggressive course, Moscow will take the necessary retaliatory measures,” Lavrov said.

But he indicated Russia wouldn’t wait forever. “We won’t allow our proposals to be drowned in endless discussions,” he said.

Amid the tensions, the U.S., Britain, Australia, Germany and Canada have moved to withdraw some of their diplomats and dependents from Kyiv, a move President Volodymyr Zelenskyy sought to play down Tuesday as part of a “complex diplomatic game.”

Read: Britain says Russia seeking to replace Ukraine government

On Wednesday, the U.S. urged Americans in Ukraine to consider leaving, saying the security situation “continues to be unpredictable due to the increased threat of Russian military action and can deteriorate with little notice.”

In 2014, following the ouster of a Kremlin-friendly president in Kyiv, Moscow annexed Ukraine’s Crimean Peninsula and threw its weight behind a separatist insurgency in the country’s eastern industrial heartland. Fighting between Ukrainian forces and Russia-backed rebels has killed over 14,000 people, and efforts to reach a settlement have stalled.

Envoys from Russia, Ukraine, France and Germany met Wednesday for more than eight hours in Paris on the separatist conflict. Although there was no breakthrough, they promised to meet for new talks in two weeks in Berlin.

The French president’s office said afterward in a statement that the parties support “unconditional respect” for a cease-fire in eastern Ukraine.

The talks focused on the 2015 Minsk peace agreement aimed at ending the conflict, and the statement didn’t address the current concerns about a Russian invasion of Ukraine.

“Those are different issues, and we didn’t discuss it,” said Kremlin envoy Dmitry Kozak.

The Ukrainian representative, Andriy Yermak, was cautiously optimistic about Wednesday’s talks, which he said marked the first major advance since December 2019. He also acknowledged they did not directly address current tensions at the border or resolve past differences.

“Of course, I wouldn’t be honest if I said that we all want faster and bigger results,” Yermak said. “And of course there is nothing bigger than the desire of Ukrainian people to stop the war, to bring back our territories and our people.”

Yermak also said the Ukrainians repeatedly raised the issue of troops now massed on the border. “This is the real threat,” he said. “I have clearly said today that we expect de-escalation not only around occupied territories but also in general de-escalation around Ukrainian borders.”

Kozak said varying interpretations of the Minsk agreement have remained a major stumbling block. He said the the four parties will make another attempt to reach consensus on the issue in two weeks.

Kozak reaffirmed that Russia isn’t a party to the conflict and emphasized that Ukraine is reluctant to engage in talks with separatists as stipulated in the Minsk document. He said there has been no progress on key aspects of the agreement that Ukraine must grant special status to the rebel regions, followed by elections.