KYIV, Ukraine - Half of Western military aid to Kyiv is delivered later than promised, delays that hobble Kyiv's ability to defend itself against Russian attacks and cost Ukrainian lives, the country's Defence Minister Rustem Umerov said on Sunday.

Ukraine, which is struggling with an ammunition shortage, has for months said that Western aid is too slow to reach it and that the hold-ups have real consequences as the war against Russia enters its third year.

"At the moment, commitment does not constitute delivery," Umerov said during a forum dedicated to the second anniversary of Russia's invasion.

"Fifty percent of commitments are not delivered on time," he added.

Europe has admitted it will fall far short of a plan to deliver more than one million artillery shells to the country by March, instead hoping to complete the shipments by the end of the year.

Umerov said such delays put Ukraine at a further disadvantage "in the mathematics of war" against Russia, which the West has said is increasingly building a war economy.

Umerov said that delayed aid will mean Kyiv will "lose people, lose territories", especially given Russia's "air superiority".

"We do everything possible and impossible but without timely supply it harms us," he said.

- 'US will not abandon Ukraine' -

Kyiv has in recent weeks been weakened by an ammunition shortage, with a vital $60-billion US aid package blocked by political wrangling in the US Congress.

US President Joe Biden said the hold-ups directly contributed to Ukraine being forced to withdraw from the frontline town of Avdiivka earlier in February -- handing Russia its first territorial gain in almost a year.

Ukraine's Prime Minister Denys Shmygal said Sunday he was "deeply convinced that the US will not abandon Ukraine in terms of financial, military and armed support."

President Volodymyr Zelensky had pressed G7 leaders on Saturday to ensure the fast delivery of weapons.

The Ukrainian leader sought to rouse the country's military and political backers on the two year anniversary of Russia's invasion, telling them: "Putin can lose this war" and "we will win."

During a Sunday service in the Vatican, Pope Francis called for intensified efforts to find a "just and lasting peace" to the conflict.

"There have been so many victims, so many wounded, so much destruction, so much anguish and so many tears over what has become a terribly long period -- the end of which we cannot yet foresee," he said.

After a year of static frontlines, Russia has in recent weeks been seeking to press its advantage on the battlefield.

- Aid not 'in vain' -

Moscow's forces are trying to advance beyond the recently captured Avdiivka, where exhausted Ukrainian troops say delays to Western aid are hobbling their ability to hold off Russian attacks.

"Despite the difficult situation, our soldiers courageously hold their lines and positions," Ukraine's commander-in-chief, Oleksandr Syrsky, said Sunday after visiting frontline command posts.

Russia marked the start of the war's third year with a wave of overnight missile and drone attacks.

A missile strike on the eastern city of Kostyantynivka wounded one, destroyed the railway station -- which is not in use -- along with dozens of apartments, shops and administrative buildings, Ukrainian authorities said.

Explosives dropped by a Russian drone killed a 57-year-old man in Nikopol, across the Dnipro river from the Zaporizhzhia nuclear power plant, captured by Russia at the start of the war.

Umerov said Russia had fired more than 8,000 missiles at his country since the start of the invasion -- an average of more than ten a day.

Visiting the southern city of Mykolaiv, Annalena Baerbock, Germany's foreign minister, pledged an additional 100 million euros ($108 million) in humanitarian aid to Kyiv.

"We should not minimise this aid as being in vain -- it saves lives every day," she said, standing in front of a building destroyed by Russian strikes on the city.