Ukraine's President Volodymyr Zelenskyy has called for continued military assistance from the West as his country's fight against Russia's invasion enters what he referred to as a crucial third year.

Zelenskyy spoke to Ukrainian and foreign reporters at a two-hour news conference in the capital, Kyiv, on Sunday, a day after the second anniversary of the start of the invasion.

He revealed for the first time that 31,000 Ukrainian soldiers had been killed in the two years, and expressed frustration with delayed military assistance from Western countries.

The Ukrainian president said, "Now is the most difficult moment for our unity."

He also referred to the stalemate in the US Congress over the country's new military aid to Ukraine. He said that US lawmakers know Ukraine needs support within a month, and that he is sure they will make a positive decision.

Zelenskyy also said Russia will prepare counteroffensive actions at the start of summer or end of May, stressing that the way the war ends will depend on this year. He said that the third year is a turning point.

The president also referred to Moscow's suspected procurement of Iranian and North Korean weapons.

He said that if Russia is taking on those weapons, it means that this year is also a crucial year for them as they also have a big deficit.

Zelenskyy noted that he hopes leaders of Western and emerging countries gather in Switzerland this spring to discuss a peace plan proposed by Kyiv that includes the withdrawal of Russian troops from Ukraine.

He said that Ukraine will propose a platform on which Russian President Vladimir Putin will be able to accept that he lost this war and that it was an error.