The United Kingdom is set to share classified weapons information with Ukraine to enable it to produce its own version of the Storm Shadow long-range cruise missile, designed jointly with France, as Prime Minister Andy Burnham visits Kyiv on his first foreign trip as the UK’s prime minister.

Burnham’s trip on Monday, timed to coincide with Ukraine’s 35th anniversary of independence from the Soviet Union, is the latest show of support on the part of the UK and Ukraine’s other European allies at a time when backing from the United States has been erratic, analysts said.

Burnham described Russia’s war on Ukraine as “four and a half years of Russia’s full-scale invasion … aimed at crushing the independence we are here to celebrate” as he appeared alongside Ukrainian President Volodymyr Zelenskyy at a ceremony in Kyiv.

“But today and every day, you prove that they have failed.”

Burnham is also to co-chair a meeting of the so-called Coalition of the Willing, those nations prepared to provide support for war-torn Ukraine.

The sharing of top-secret weapons blueprints stands in contrast to US President Donald Trump’s backpedalling last month on a promise to allow Ukraine to manufacture its own version of the US-made Patriot air defence interceptor, which Ukraine says it badly needs to counter Russian ballistic missile attacks.

While the US has provided Ukraine with US-made Patriot air defence batteries and munitions in the past, Trump last month said handing over the underlying technology to Ukraine to be able to independently produce them was “a hard thing to give away”.

The UK’s decision to share blueprints, however, follows a similar move by France and comes as Ukraine and Russia exchange heavy air attacks and Russian President Vladimir Putin warns of intensified retaliatory strikes on Ukrainian economic infrastructure.

Ukraine has stepped up its domestic military production, crafting long-range drones and missiles that strike deep into Russian territory, but analysts said producing its own Storm Shadows will give Kyiv the ability to hit Russia’s strategic targets more efficiently and at an unprecedented rate.

What are Storm Shadow long-range missiles?

Also known as SCALP in France, these missiles have a range of about 560km (350 miles) and are capable of hitting targets 240km (150 miles) inside Russian territory. This is not as far as Ukraine’s in-house, deep-strike drones, such as the FP-5 Flamingo cruise missile, which has a range of 3,000km (1,865 miles).

But while Ukrainian long-range missiles can hit “soft” targets inside Russia, such as Wildberries warehouses, Storm Shadow missiles give Kyiv the ability to hit “hard” targets, including heavily fortified, guarded locations that are usually protected by much tougher defences.

Their advanced navigation systems also mean they can be used at night and in all weather conditions.

Last year, the Ukrainian military’s General Staff said Storm Shadow missiles made by the manufacturer MBDA and provided by the UK had been used to hit Russian facilities, including a chemical plant and the Novoshakhtinsk oil refinery, one of the biggest oil product suppliers in southern Russia. This year, they were used to attack Russia’s Black Sea naval headquarters in the port city of Sevastopol in Crimea.

One Storm Shadow missile is estimated to cost about $1m to produce, so they are deployed in more carefully calibrated attacks than the flurry of cheap drones that Ukraine already mass-produces.

How easy will it be for Ukraine to build its own Storm Shadow missiles?

Keir Giles, an associate fellow at the Chatham House think tank, said Ukraine is likely to have a good capacity for producing these more sophisticated weapon systems once it has the blueprints.

“Ukraine, under the force of fighting a war of national survival, has been developing a very agile, highly motivated and distributed defence industry, which is far ahead in terms of adaptation to current needs [compared with] some of its Western European counterparts, including the UK,” he told Al Jazeera.

Being able to produce higher quantities of this missile, more than its actual capability, is what could make the difference, he added.

“Ukraine has had to be highly selective in the targets against which it uses its very limited stocks of the most advanced weapons systems,” Giles said. “Russia, meanwhile, has been exponentially increasing its production of drones and missiles, a trend that’s been in place for several years now.”

“So redressing that balance would be a major step forward for Ukraine, especially if it is able to reduce the number of missiles being launched at Ukraine every night by striking at the facilities that enable those launches,” the analyst added.

Has Ukraine been able to produce any of its own long-range missiles?

Yes. Besides its mass production of cheap short-range drones and interceptors, Ukraine is capable of designing and manufacturing more sophisticated longer-range missile systems, including the Neptune and Flamingo cruise missiles.

Karan Vassil, a Eurasia analyst at the UK-based private intelligence firm Sibylline, said Ukraine has also been developing and testing its own ballistic missile systems.

However, the Storm Shadow/SCALP “is a highly sophisticated weapons system incorporating decades of Anglo-French research and development”, Vassil told Al Jazeera. “Licensed production gives Ukraine access to knowledge and industrial processes that would otherwise take considerable time and resources to reproduce.”

Giles, who also leads the Conflict Studies Research Centre, a group of experts in Eurasian security, said Ukraine may well already have knowledge of the design of Storm Shadow missiles but using it without cooperation would be a “slap in the face to its coalition supporters”.

The reason Ukraine is only now getting access to the missiles’ blueprints has to do with politics, he said. “The United States is not willing to supply the interceptors for Patriot missile systems, so there’s a gap in Ukraine’s air and missile defences, which Russia has been exploiting.”

He added: “European partners are taking up the task of making sure that Ukraine can prevail in the war, and a major part of that is ensuring that it can strike into Russia.”

Vassil said British and French willingness to transfer classified missile-production knowledge sets a potentially important precedent for future allied cooperation. “But it remains uncertain whether this will have an impact on Washington’s posture regarding Patriot interceptors,” he said.

How fast can Ukraine scale up production of Storm Shadow missiles?

France and the UK have expressed hope that they can help Ukraine set up a production line by the end of the year.

However, estimates suggested a new batch of cruise missiles of this complexity could take about two years from contract award to delivery, according to Vassil, who added that establishing production will be a challenging endeavour and will most likely continue to depend on a complex international supply chain.

Storm Shadows also incorporate some sensitive US technologies, meaning some aspects of supply or transfer may still require US approval and “it remains uncertain how this will apply to Ukrainian production”, he said.

There are also substantial security challenges. “Missile-production facilities inside Ukraine would present valuable targets for Russia and would have to operate under the continuing threat of Russian long-range missile and drone attacks,” Vassil continued.

“Protecting production sites, dispersing manufacturing and maintaining supplies of critical components could, therefore, become almost as important as obtaining the technical information itself.”