U.S. President Joe Biden and other G-7 leaders are set to unveil future support for Ukraine on Wednesday after the conclusion of a high-stakes NATO summit in Lithuana's capital.

"President Biden and G-7 leaders will make a major announcement alongside President Zelenskyy this afternoon outlining our long-term commitments to support the people of Ukraine," U.S. National Security Council Senior Director for Europe Amanda Sloat said during a press briefing in Vilnius on Wednesday morning. "The United States, along with G-7 leaders, will announce our intent to help Ukraine build a military that can defend itself and deter a future attack."

"The launch of this process today will start a series of bilateral negotiations with Ukraine on the reaching of bilateral security commitments to help make this a reality," she added. "In particular, this process will ensure that the military assistance we provide Ukraine to defend itself against Russian aggression continues to be part of a long-term investment in Ukraine’s future force."

That investment will include making sure "Ukraine has a sustainable fighting force capable of defending Ukraine now and deterring Russian aggression in the future, a strong and stable economy, and the help Ukraine needs to advance the reform agenda to support the good governance necessary to advance Ukraine's Euro-Atlantic aspirations, which Ukraine recommits itself to as part of this declaration," according to Sloan.

"Taken together, we believe the declaration we will announce today seeks to ensure Ukraine's future as a free, independent, democratic, and sovereign nation," she told reporters. "This multilateral declaration will send a significant signal to Russia that time is not on its side."

-ABC News' Molly Nagle

Russian Defense Minister Sergei Shoigu made his first public comments since last month’s failed rebellion led by Wagner Group boss Yevgeny Prigozhin and claimed that Russian President Vladimir Putin is actively engaged with his commanders
Shoigu said that Putin listens to "very detailed reports" twice a day and "all commanders on all levels understand and feel all the weight of responsibility that was placed on them."

"They carry out their responsibilities with great pride," he said.

Shoigu claimed that Ukraine hasn't achieved any of its goals in its counteroffensive. The defense minster added that Russia may be using cluster munitions following the announcement that Ukraine will be receiving similar weapons from the U.S.

"If the United States supplies cluster munitions to Ukraine, the Russian Armed Forces will be forced to use similar weapons against the Armed Forces of Ukraine as a response," he said.

-ABC News' Natalia Shumskaia, Ellie Kaufman and Will Gretsky

Russia will take “early and adequate measures” in connection with Sweden and Finland joining NATO, Russian Foreign Minister Sergei Lavrov said Tuesday after the start of the NATO summit in Vilnius, Lithuania.

Lavrov told reporters that he is convinced that "the speed with which this happened, of course, forces us to look for the reason in the complete subordinate position in which these countries have placed the United States and the rest of the collective West,” according to the Russian news agency Interfax.

-ABC News' Natalia Shumskaia and Ellie Kaufman

Ukraine will get an invitation to join NATO when all the allies agree and all the conditions are met, Secretary General Jens Stoltenberg said during a press conference from the NATO summit in Vilinus, Lithuania, on Tuesday.

NATO agreed to remove the required membership action plan, he added, which makes the process take only one step instead of two.

A NATO-Ukraine Council will also be launched, Stoltenberg announced. The first session is planned for Wednesday with participation from Ukrainian President Volodymyr Zelenskyy, he said.

Zelenskyy had criticized the process for joining NATO ahead of his trip to Lithuania, saying, "It’s unprecedented and absurd when timeframe is not set neither for the invitation nor for Ukraine's membership."

-ABC News' Fidel Pavlenko

The United States "is prepared to defend every inch of NATO territory," National Security Advisor Jake Sullivan said Wednesday, amid Russia's threats of military retaliation if Sweden and Ukraine officially join the alliance.

"At the end of the day, Russia does not get a vote in who joins NATO," Sullivan told ABC News' George Stephanopoulos during an interview Wednesday on "Good Morning America."

"If Russia does choose to test Article 5, President Biden has said he is prepared to defend every inch of NATO territory," he added. "And later tonight, when he addresses a large crowd in Vilnius in a speech about his vision for Euro-Atlantic security and for American leadership, he will reinforce this point about the sanctity of Article 5."

Article 5 of the NATO treaty states that the signed parties "agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all."

Sweden and Finland, which have historically embraced neutrality, applied for NATO membership together last year despite warnings from Moscow against doing so, as Russian forces invaded Ukraine. Finland officially joined the alliance in April following Turkish ratification, but Turkey and Hungary have yet to ratify Sweden’s membership. NATO Secretary-General Jens Stoltenberg announced Monday that Turkish President Recep Tayyip Erdogan has agreed to send Sweden’s NATO accession documents to Turkey’s Parliament for approval "as soon as possible," one of the last steps in the membership process.

Meanwhile, Ukraine is pushing hard for NATO membership as Russia’s war presses on. Stoltenberg announced Tuesday that the bloc "will issue an invitation for Ukraine to join NATO when allies agree and conditions are met," pledging to speed up the process by eliminating bureaucratic hurdles, but without offering a timeline.

"All 31 allies got together yesterday to say with one voice that Ukraine's future is in NATO. The real question is just how we work down the pathway to get them in," Sullivan told ABC News on Wednesday. "So the signal that NATO sent yesterday was very positive to Ukraine about its future prospects for joining NATO, and we will work in terms of the democratic and security sector reforms that are necessary. And in the meantime, we're not just going to sit around. We're going to provide Ukraine with the weapons and military assistance it needs to defend its territory against Russia and to deter future aggression from Russia."

Ukraine has requested F-16 fighter jets and long-range missiles to aid its counteroffensive against Russian forces. Sullivan said the U.S. has already taken steps with NATO allies to begin the training of Ukrainian pilots on F-16s, which "will take some time," and then the aircraft will be transferred to Ukraine "likely from European countries that have excess F-16 supplies." As for the long-range missiles, Sullivan said the U.S. will continue to look into the issue and discuss it with Ukraine.