President Volodymyr Zelenskiy has signed a bill to lower the mobilisation age for combat duty from 27 to 25, a move that should help Ukraine generate more fighting power in its war with Russia.

The move expands the number of civilians the army can mobilise into its ranks to fight under martial law, which has been in place since Russia launched its full-scale invasion in February 2022.

The bill had been on Zelenskiy’s table since it was approved by lawmakers in May 2023, and it was not immediately clear what prompted him to sign it. Parliament has been discussing a separate bill to broadly tighten draft rules for months.

Zelenskiy separately signed a second bill requiring men who were given military waivers on disability grounds to undergo another medical assessment.

A third bill he signed aimed to create an online database of those eligible for military service. Both those bills could potentially help the military draft more fighters.

A string of strict measures set out in an earlier draft of that bill were gutted following a public outcry.

Ukrainian troops face challenges on the battlefield, with a shortage of ammunition supplies and vital funding from the US blocked by Republicans in Congress for months, as well as the European Union failing to deliver promised ammunition on time.

The signing of the mobilisation age legislation was not immediately announced by the president’s office. Parliament merely updated the entry for the bill on its website to read: “returned with the signature of the president of Ukraine”.

Zelenskiy said late last year that he would sign the bill only if he was given a strong enough argument of the need to do so.

The Ukrainian leader said in December that the military had proposed mobilising up to 500,000 more Ukrainians into the armed forces, something he said the then-commander of the armed forces had asked for.

Since then, Ukraine has changed the head of the armed forces and the new chief, Oleksandr Syrskyi, said last week that the figure was no longer up to date and that it had been “significantly reduced” after a review of resources.

Zelenskiy has warned that Russia may plan another offensive in the coming months, and Kyiv’s troops have been scaling up their efforts to build up strong defensive fortifications along a sprawling front line.

With the initial shock of the invasion long gone, Ukraine has faced a significant reduction in the flow of volunteer fighters and numerous cases of draft evasion have been reported.