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

Russian President Vladimir Putin has been briefed by the country's security agencies about what was referred to as an "attempted armed rebellion," according to Russia's state-run media.

The late-night statement from Putin's spokesman suggested that the Kremlin considered Wagner Group's move into Rostov-on-Don, a key Russian city close to the border with Ukraine, to be a "rebellion."

Wagner's founder Yevgeny Prigozhin in an audio message on Friday claimed his forces would now punish Russia's defense minister and chief of general staff, telling other units to stand down and not offer resistance.

"Special services, law enforcement agencies, namely the Ministry of Defense, the FSB, the Ministry of Internal Affairs, Rosgvardiya, in round-the-clock mode, constantly report to the president on the measures taken in the context of the implementation of the instructions previously given to him," Kremlin spokesperson Dmitry Peskov said on Saturday.

-ABC News' Tanya Stukalova and Patrick Reevell