KYIV, Ukraine — Peace negotiations are usually thought to involve two sides brought together by a mediator trying to tease out possible compromises, far from the anger and destruction of the battlefield.

But the latest talks on the eight-year-old war in Ukraine are different. The conflict — and an overtly threatened Russian invasion that the talks are intended to forestall — is in Ukraine. Ukraine, however, will be missing from two of the three negotiating sessions scheduled for this week.

Such a limited role for Ukraine in the talks has clearly unnerved the government in Kyiv. Fearing the talks will yield little or nothing, and with President Biden’s statement that the United States will not intervene militarily if Russia invades, Ukraine has quietly pursued its own negotiating track with Moscow.

The latest threat of invasion began last month, when Russia massed more than 100,000 troops along its borders with Ukraine and demanded wide-ranging — and, to Western analysts, impossible — concessions from the United States and NATO on matters of European security.

Those were laid out in two draft treaties proposed by Moscow that the government in Kyiv — because it is not a member of the alliance — has no say over. President Vladimir V. Putin of Russia subsequently threatened to launch an invasion of Ukraine if the talks on its proposals should fail.

In effect, that made Ukraine “the hostage,” of Russia, said Kostiantyn Yelisieiev, a former Ukrainian ambassador to the European Union.

Moscow’s sidelining of Ukraine and its demand for direct talks with the United States and NATO were intentional, Mr. Yelisieiev said.

One of Russia’s key demands is that NATO exclude any possibility of Ukraine’s membership in the alliance — NATO has already rejected that demand — and halt all military cooperation with the country. Russia also insisted that the alliance halt all military activities throughout Eastern Europe and Central Asia.

The talks got off to a rocky start on Sunday when a senior Russian official warned that the United States had a “lack of understanding” of the Kremlin’s security demands, and the United States voiced doubts over whether Russia was “serious” about de-escalating the crisis in Ukraine.

In remarks reported by Russian news agencies, Deputy Foreign Minister Sergei A. Ryabkov said he was intent on negotiating “dynamically, without pauses,” to prevent the West from “putting the brakes on all this and burying it in endless discussions.”

In appearances on Sunday morning’s network news shows, Secretary of State Antony J. Blinken said the United States was “not about making concessions” under the threat of a Russian invasion of Ukraine, eight years after it annexed Crimea.

“It’s about seeing whether, in the context of dialogue and diplomacy, there are things that both sides, all sides can do to reduce tensions,” he said on CNN. “We’ve done that in the past.”

The current threat to Ukraine follows eight years of low-level conflict. Russia intervened militarily in Ukraine in 2014, annexing the Crimean Peninsula and fomenting separatist uprisings in two eastern provinces, leading to the deaths of more than 13,000 people.

“The issues concern all of Europe, including Ukraine, but Putin suggests discussions between Russia and the United States,” Mr. Yelisieiev said. “Russia in this way made an announcement of a sphere of influence. ‘You leave us the former Soviet space and do what you want elsewhere.’”

A Ukrainian delegation will take part in the third of the three rounds of talks, scheduled for Thursday in Vienna under the auspices of the Organization for Security and Cooperation in Europe. The United States has said it is coordinating closely with the authorities in Kyiv, and Mr. Biden spoke on the phone with President Volodymyr Zelensky of Ukraine a week ago.

“No decisions about Ukraine without Ukraine,” the Ukrainian foreign minister, Dmytro Kuleba, posted on Twitter last week, noting he will also meet with NATO officials in Brussels. “Part of a wide diplomatic effort to deter further Russian aggression.”

Given the stakes for Ukraine, the Zelensky government has decided not to rely wholly on the U.S.-led negotiations. Mr. Zelensky announced a separate, Ukrainian diplomatic initiative with Russia in late December, the specifics of which were later published in the Russian newspaper Kommersant.

The 10-point Ukrainian plan, which is bound to be highly contentious in Ukraine, begins with three confidence-building steps — a cease-fire, an exchange of prisoners and the opening of crossing points for civilians on the front line in the eastern Ukraine war — then moves to political issues. The first point, the cease-fire, has already been implemented.

The political matters involve direct talks between Mr. Zelensky and Mr. Putin and a final point, No. 10, under which the Ukrainian government would submit to Parliament laws granting self-rule to separatist areas and devolving some powers to these areas, according to Kommersant.

In the Russian interpretation, these laws would grant its proxies in eastern Ukraine veto power over foreign policy decisions by the central government, including NATO membership for Ukraine, potentially satisfying enough of Russia’s request to forestall a catastrophic war in Ukraine.

Western diplomats say the proposed laws leave wiggle room for interpretation, and that Mr. Zelensky is unlikely to grant Moscow veto power over future NATO membership. The proposal says nothing about the aspiration for NATO membership written into Ukraine’s Constitution and has seemingly stalled after the cease-fire, announced on Dec. 22.

Like so many other diplomatic efforts to end the war, this one is given little chance of success by most analysts, but it could serve other purposes. Ukraine can do “nothing” in diplomacy but wait for the possible outbreak of violence, said Oleksandr Danylyuk, a former secretary of the Ukrainian Security Council. “This is why Putin is doing this. It’s his goal to show that Ukraine cannot do anything.”

And the negotiating effort could have one lasting effect: Mr. Zelensky’s apparent willingness to negotiate over autonomy for the separatist regions and any hint of accepting neutrality between the West and Russia could cause a firestorm in Ukrainian politics.

To date, none of the diplomatic talks with Russia, whether with the United States or Ukraine, have slowed the stream of ominous statements from Russian officials that diplomats and analysts worry could be used to justify military action or prepare the Russian population for a war.

In July, Mr. Putin published an article arguing that Russia and Ukraine are essentially the same country, with a shared history and culture, suggesting a reason for unification.

The threats became more focused in August after the American withdrawal from Afghanistan, when senior Russian security officials publicly taunted Ukraine that it, too, could soon lose the United States as a protector.

“The country is headed toward collapse, and the White House at a certain moment won’t even remember about its supporters in Kyiv,” Nikolai Patrushev, the secretary of Russia’s Security Council, told Izvestia newspaper soon after the fall of Kabul.

In December, Mr. Putin, speaking to a gathering of generals and security officials, said Moscow might resort to “military-technical” means if Western nations “continue the obviously aggressive stance.”

A deputy foreign minister for Russia, Aleksandr Grushko, more explicitly linked a threat of Russian military force to a breakdown in the talks.

“The Europeans must also think about whether they want to avoid making their continent the scene of a military confrontation,” Mr. Grushko said. “They have a choice. Either take seriously what is put on the table or face a military-technical alternative.”

Echoing American claims used to justify the invasion of Iraq in 2003, the Russian defense minister, Sergei K. Shoigu, claimed without providing evidence that Moscow had intelligence showing that American mercenaries had brought an “unidentified chemical component” into Ukraine.

Pro-Kremlin commentators have cheered the Kremlin’s tough stance as a Russian nationalist triumph.

One newspaper compared Moscow favorably to a gangster character in a Russian movie who, “raising his heavy fist and looking into the eyes of his interlocutor, gently asks again: Where is your strength America?”