The British government announced on Thursday it was giving long-range cruise missiles to Ukraine to help drive out Russia’s occupying forces, just as Kyiv delayed a possible counteroffensive more than 14 months after the Kremlin’s full-scale invasion as it awaits the delivery of more western weapons.

UK defence secretary Ben Wallace told lawmakers in the House of Commons that Britain is donating Storm Shadow missiles, a conventionally-armed deep-strike weapon with a range of more than 250km.

That means it can hit targets deep behind the front line, including in Russia-occupied Crimea. UK media reported that Ukraine has pledged not to use the missiles to attack Russia itself. Wallace said the missiles “are now going into or are in the country itself”.

Ben Hodges, a former US army Europe commanding general, tweeted: “Well done UK!” “This will give Ukraine the capability to make Crimea untenable for Russian forces” and would force a Russian rethink of where to position its Black Sea fleet, he added.

The British move gives another boost to the Ukrainian military after it received other advanced western weapons including tanks and long-range precision artillery.

The announcement came shortly after UkrainianPresident Volodymyr Zelensky said his country’s military needs more time to prepare an anticipated counteroffensive aimed at pushing back Russian occupying forces and opening a new chapter in the war more than 14 months after the Kremlin’s full-scale invasion.

Zelensky said in an interview broadcast on Thursday by the BBC that it would be “unacceptable” to launch the assault now because too many lives would be lost.