KYIV (Reuters) - Ukrainian President Volodymyr Zelenskiy said it would be absurd if Ukraine is not offered a timeframe for NATO membership at an alliance summit starting in Vilnius on Tuesday.

"It’s unprecedented and absurd when (a) time frame is not set, neither for the invitation (to join NATO) nor for Ukraine's membership. While at the same time vague wording about 'conditions' is added even for inviting Ukraine," he wrote in English on the Telegram messaging app.

He said lingering uncertainty over Ukraine's NATO membership would provide Russia with "motivation to continue its terror." Indicating that he would attend the summit, he said: "Uncertainty is weakness. And I will openly discuss this at the summit."

(Reporting by Anna Pruchnicka, Writing by Olena Harmash, Editing by Timothy Heritage)