Speaking at the Munich security conference on Saturday, Zelensky pointed out that in 1994 Ukraine joined the Budapest Memorandum and gave up its nuclear weapons in exchange for security guarantees, suggesting the move could be reversed if it is threatened by neighboring Russia, RT reported.

“Today we have neither weapons nor security. We have lost a part of our territory, which is larger by its area than Switzerland, the Netherlands, Belgium. And, most importantly, we’ve lost millions of our citizens. All this is absent,” Zelensky said.

He also added that Ukraine tried to initiate consultations with the guarantor states of the Budapest Memorandum three times as part of an effort to review its terms – without any success.

“Today Ukraine will do it for the fourth time,” he stated, stressing that he had ordered his Foreign Minister Dmitry Kuleba to request the consultations but that it would be the last attempt from Ukraine's side.

“If they do not take place or there are no concrete decisions regarding the security guarantees for our state, Ukraine will have every right to believe that the Budapest Memorandum is not working and all package decisions of 1994 have been put under question,” Zelensky continued.

The Ukrainian leader underlined that “collective condemnation” by Western allies has not turned so far into “collective actions".

Replying to questions after the speech, Zelensky added that he did not agree with “a leader of one major country” on the matter of potential sanctions against Russia. He explained his discontent with his counterpart’s remarks by saying, “We do not need sanctions when we are already shelled, when the borders disappear, when our country is already occupied. What is the benefit of these sanctions for us afterwards?”

Over the last few months, Western countries have repeatedly accused Russia of alleged plans to invade Ukraine – something that Moscow categorically denies. On Friday, the authorities of two breakaway regions in Eastern Ukraine claimed that Kiev planned a military “breakthrough” into their territory. Ukrainian officials have also denied these claims.

Zelensky insists that the Minsk agreements, which are poised to serve as a road map for a peace process, have been “poorly written” and do not benefit Ukraine. Instead Zelensky would like to see a new document, to be signed by the “major powers”, including Russia and the US, which would contain several clauses on security guarantees for Ukraine.

Zelensky has also thanked US Vice President Kamala Harris for Washington’s support amid the standoff between Moscow and the West over his country. At the same time, however, he also called on the US to make more concrete commitments to Kiev.

Speaking before a closed-doors meeting with Harris at the Munich Security Conference in Germany on Saturday, Zelensky said that he is “very grateful to the United States”, which has ramped up military aid to Ukraine in recent weeks, and vowed to sanction Moscow should Russian President Vladimir Putin invade the country.

Ukraine’s army, he added, is “defending all of Europe".

While Zelensky and top Kiev officials have presented Moscow as poses a military threat to the whole continent, the Joe Biden administration still insists it would not respond to a hypothetical Russian invasion with American boots on the ground in Ukraine. Speaking alongside Zelensky on Saturday, Harris offered no departure from this policy, instead threatening Russia with “swift and severe economic sanctions".

US officials have predicted several possible start dates for a Russian invasion of Ukraine, all of which have thus far passed without incident. In a separate speech on Saturday, Zelensky seemingly expressed frustration with Washington’s continued making of predictions. 

“To help Ukraine, there is no need to constantly talk about possible invasion dates,” he said.

"You're telling me that it's 100% that the war will start in a couple of days. Then what [are you] waiting for?” he added, calling on Western leaders to sanction Russian before the outbreak of hostilities.

Russia has denied it has plans to invade Ukraine, and dismissed Washington’s failed predictions, including those from President Biden himself, as “hysteria” and “fake news".

In the past several days, violence has flared up in Eastern Ukraine.

Kiev has also denied it has any plans to retake Donetsk or Lugansk by force, and Zelensky insisted on Saturday that Ukraine is “longing for peace”. However, Moscow has called on Ukraine to achieve this peace by abiding by the 2015 Minsk agreements, which call for a permanent ceasefire and some autonomy for the breakaway regions. 

Western leaders have called on Putin to withdraw troops stationed within Russia near Ukraine’s borders, but have refused to take NATO membership for Ukraine off the table, despite Moscow for decades insisting that the alliance on its doorstep would present an unacceptable security risk.