But Zelensky insisted the move -- part of a drive to modernise the 250,000-strong military -- did not mean a large-scale invasion by Moscow was imminent amid fears over a massive buildup of Russia troops at Ukraine's borders.

Ukraine's armed forces have undergone major improvements since Russia annexed the Crimean peninsula without a fight in 2014 and began fuelling a separatist conflict that has cost more than 13,000 lives.

Zelensky signed a decree to add 100,000 personnel over the next three years, create 20 new brigades and improve the pay and living conditions for servicemen.

He also ordered the government to draft legislation to end obligatory military service for young men by 2024 as Kyiv looks to professionalise its forces.

"The decree is not because there will soon be war. But for us to have peace in the future," Zelensky said.

Ukraine's armed forces have been transformed with Western support during the past eight years from a threadbare outfit that relied on volunteer fighters to plug the gaps to a battle-hardened force.

"I want to assure you that today Ukraine has a stronger army than ever," Ukrainian Prime Minister Denys Shmygal said at a meeting with his Polish counterpart.

Ukraine's allies, led by the United States, have scrambled to send more arms to Kyiv in recent weeks as they warn Moscow could be planning a full-scale invasion after massing over 100,000 troops on the boder.

Defence Minister Oleksiy Reznikov on Tuesday welcomed a sixth plane carrying ammunition from the US, saying it brought recent deliveries from Washington to about 500 tonnes of materiel.

The influx of fresh arms including anti-tank missiles adds to key firepower acquired by Kyiv such as attack drones brought from Turkey.

But despite the improvements and new hardware, the country's military still remains massively outnumbered and outgunned by Russia's armed forces.