An in-person meeting between Ukrainian President Volodymyr Zelenskyy and U.S. President Joe Biden is currently underway in Lithuania's capital.

Zelenskyy took to Twitter on Wednesday evening to announce that their bilateral meeting in Vilnius "has begun." It's the third face-to-face meeting to take place between the two leaders this year.

"The focus is on security and everything that enhances it," Zelenskyy tweeted. "It will be meaningful."

In a joint declaration released Wednesday, the leaders of the Group of Seven reaffirmed their "unwavering commitment to the strategic objective of a free, independent, democratic and sovereign Ukraine."

"We will stand with Ukraine as it defends itself against Russian aggression, for as long as it takes," the joint declaration states.

G-7 leaders wrote in the joint declaration that they are working to "formalize" their "enduring support to Ukraine as it defends its sovereignty and territorial integrity, rebuilds its economy, protects its citizens, and pursues integration into the Euro-Atlantic community."

They also said they will "work with Ukraine" on an "enhanced package of security commitments and arrangements in case of future aggression to enable Ukraine to defend its territory and sovereignty."

The G-7 is an intergovernmental political forum consisting of Canada, France, Germany, Italy, Japan, the United Kingdom and the United States.

-ABC News' Ellie Kaufman

Ukrainian President Volodymyr Zelenskyy applauded the "outcome" of the annual NATO summit on Wednesday, describing the new commitments to his country as a "significant security victory."

"Ukrainian delegation is bringing home significant security victory," Zelenskyy said in brief remarks alongside world leaders in Lithuana's capital. "For our country, for our people, for our children."

Zelenskyy's laudatory tone was a sharp departure from his comments on Twitter the previous day. He told reporters that the long-term commitments announced by G-7 leaders on Wednesday would "absolutely" open "new security opportunities" and that he was "grateful."

"I thank everyone who made it possible," he added.

-ABC News' Cheyenne Haslett

G-7 leaders including U.S. President Joe Biden stood alongside Ukrainian President Volodymyr Zelenskyy in Lithuania's capital on Wednesday to announce a new long-term security package for Ukraine's future, while reaffirming that Kyiv has a place in NATO -- but not yet.

"All our allies agreed Ukraine's future lies in NATO. That's not a surprise to any of us, I don't think. I hope it's not a surprise to you, Mr. President," Biden said, turning to Zelenskyy during the press conference in Vilnius.

"Ukraine continues to make progress on necessary reforms," he added. "But we're not waiting for that process to be finished to make the long-term commitments that we're making to Ukraine security."

The U.S. commander in chief said he and Zelenskyy discussed what guarantees could be made to Ukraine during his visit to Kyiv earlier this year.

"Today, the members of the G-7 are launching the Joint Declaration of Support for Ukraine to make it clear that our support will last long into the future," Biden told reporters. "This starts the process by which each of our nations and any other nation who wishes to participate will negotiate long-term bilateral security commitments with and to Ukraine."

"We're going to help Ukraine build a strong, capable defense across land, air and sea," he added, "from which will be a force of stability in the region and deter against any and all threats."

-ABC News' Molly Nagle

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