President Volodymyr Zelenskyy again called on Tuesday for NATO to invite Ukraine to become a member, offering a strongly worded statement as the coalition leaders gathered for a summit in Lithuania.

Ukraine "deserves respect," Zelenskyy said in a statement posted on Twitter.

"It's unprecedented and absurd when time frame is not set neither for the invitation nor for Ukraine's membership," he said. "While at the same time vague wording about 'conditions' is added even for inviting Ukraine. It seems there is no readiness neither to invite Ukraine to NATO nor to make it a member of the Alliance."

Keeping Ukraine out of NATO amounts to a "motivation" for Russia to "continue its terror," he said.

"Uncertainty is weakness," he added.

Russia rebutted the statement a short while later.

"This is potentially very dangerous for European security. Indeed, it is fraught with great dangers, and those who will make this decision should be aware of that," Dmitry Peskov, a Kremlin spokesperson, said when asked to comment on Ukraine's possible fast-track admission to the coalition.

President Joe Biden will meet with Ukrainian President Volodymyr Zelenskyy at the NATO summit in Vilnius, Lithuania this week, an administration official told ABC News.

The meeting comes as Zelenskyy pushes for a spot in NATO, despite Biden's public comments this weekend that he doesn't think that's the right move at this moment.

Biden has instead suggested a relationship similar to Israel and the U.S., with strong security commitments.

-ABC News' Cheyenne Haslett and Molly Nagle

Turkey and Sweden have reached a deal to advance the latter country's bid to join NATO, according to NATO Chief Jens Stoltenberg.

"This is an historic step which makes all #NATO Allies stronger & safer," Stoltenberg tweeted along with a photo of him and the two leaders shaking hands.

Turkey and Sweden have agreed to work on "legitimate security concerns," according to NATO.

Sweden has resumed arms exports with Turkey and "will present a roadmap as the basis of its continued fight against terrorism in all its forms and manifestations," according to NATO.

The two countries agreed to set up economic cooperation through the Türkiye-Sweden Joint Economic and Trade Committee, NATO said.

-ABC News' Will Gretsky

Ukrainian President Volodymyr Zelenskyy outlined his agenda for the NATO summit in Vilnius in his evening address.

Zelenskyy said the Ukrainian government is "working to make the algorithm for gaining membership as clear and fast as possible."

The president also added, in regards to the summit, "there may be good weaponry-related news."

"The priorities are absolutely clear: air defense for our cities, for all communities throughout the country, we are working to create a full-fledged sky shield," he said.

-ABC News' Will Gretsky

U.S. President Joe Biden will make a "memorable speech" before world leaders in Lithuania's capital on the final day of a high-stakes NATO summit, according to National Security Council Senior Director for Europe Amanda Sloat.

Biden's remarks on Wednesday afternoon will focus on similar themes to what he said during his speech in Poland in late February marking one year since Russia waged war on Ukraine.

"President Biden will talk about the strength of the NATO Alliance and how it remains a force for global security and stability, as it has for more than seven decades. He'll talk about how NATO is more vital to our shared future and that didn't happen by accident," Sloat told reporters during a press briefing in Vilnius on Wednesday morning.

"As the president has talked about before, Vladimir Putin thought he could break our resolve when he invaded Ukraine. But our NATO allies and our partners around the world responded by coming together to support the brave people of Ukraine as they defend their freedom, their independence and their democracy," she added.

Beyond addressing the strength of the NATO alliance and the importance of standing by Ukraine, Biden will also look to pitch cooperation like we've seen for Ukraine to tackle other major challenges facing the world, "including the climate crisis, emerging technologies, upholding the international rules of the road and expanding opportunities so we build an economy where no one gets left behind," according to Sloat.

-ABC News' Molly Nagle