NATO Secretary-General Jens Stoltenberg warned Wednesday of the "real risk" that Russian President Vladimir Putin will advance into Europe after Ukraine.
Stoltenberg urged NATO to hold firm against Russia as it makes gains in its effort to annex parts of Ukraine, for fear of going further.
"If Putin wins in Ukraine, there is [a] real risk that his aggression will not end there," Stoltenberg told reporters during a press conference. "Our support is not charity. It is an investment in our security."
"The only way to reach a just and lasting solution is to convince President Putin that they will not win on the battlefield," he continued. "And the only way to ensure that President Putin realizes that he is not winning on the battlefield is to continue to support Ukraine."
European countries are growing more skeptical of supporting Ukraine. Slovakian Prime Minister Robert Fico, who stood beside Stoltenberg during the press conference, recently halted Slovakia's military assistance to Kyiv.
And Hungarian Prime Minister Viktor Orban has been a critical roadblock to the European Union's incorporation of Ukraine into its organization, The Guardian noted.
Ukrainian President Volodymyr Zelenskyy is still relentlessly pushing for it, urging a summit of European Union leaders on Thursday to open talks about Ukraine's membership in the EU.
"It's very important that Europe doesn't fall back into indecision today. Nobody wants Europe to be seen as untrustworthy or as unable to take decisions it prepared itself," Zelenskyy said.
"People in Europe won't understand if Putin's satisfied smile becomes the reward for a meeting in Brussels," he added.
Meanwhile, the United States is engaging in an intense battle between the Democratic-controlled Senate and Republican-led House over additional aid to Ukraine, which will likely cause further delay.
Information from The Associated Press was used in this report.