Ukraine’s planned counteroffensive to win back territory occupied by Russia has a good chance of success but may bring high casualties if Russia uses its prepared defences well, Czech president and former Nato general Petr Pavel said on Friday.

Pavel, 61, said in an interview that Ukraine needs support for Nato and European Union entry but joining either will be a lengthy process, though talks on the EU accession could start this year, Reuters reported.

Pavel, who was Czech army chief and also the principal military adviser to the Nato secretary-general in 2015-2018, said Ukraine would eventually get western fighter jets it has been calling for but it was impossible to deliver them in time for the upcoming offensive, and there were higher priorities such as ammunition.

“There is certainly high hope that the Ukrainian counteroffensive will be successful, because Ukraine is motivated, well prepared, its troops are experienced and certainly do not succumb to such deficiencies as the Russian army,” Pavel said at Prague Castle, the seat of the Czech presidency.

The Russian army had severe problems in logistics and morale, but a collapse of defences should not be expected, he said.

“Russia has had time to prepare a relatively high-quality and in-depth defence in several lines, which, if used effectively, will cost … Ukraine large casualties,” he said.

It was impossible to say what size of territory Ukraine could win back as various scenarios were open, he said. “Things do not always go according to wishes and plans but I think that the chance for a significant Ukrainian success is really high.”

A Russian defeat in Ukraine will not derail China’s rise, while relations between Beijing and the EU will be “critically affected” if Xi Jinping does not push Vladimir Putin to withdraw his forces, European ministers have been told.

The message comes in a paper drawn up by the EU foreign policy chief, Josep Borrell, who is meeting the EU’s 27 foreign ministers on Friday in Stockholm to discuss how the bloc should “recalibrate” its policy towards Beijing.

Along with the war in Ukraine, relations with China have become Europe’s most pressing foreign policy issue, but EU politicians take different approaches on how to respond to an increasingly repressive and nationalistic Beijing – revealed in the furore over Emmanuel Macron’s comments about not being drawn into a US-China clash over Taiwan.

In a letter to ministers to accompany the paper, Borrell highlights at least three reasons to adjust the EU’s approach: China’s internal changes “with nationalism and ideology on the rise”; the “hardening of US-China competition” in all areas and China’s status as a key regional and global player.

Two Russian pilots were killed on Friday when a Russian Mi-28 military helicopter crashed in the annexed peninsula of Crimea, Russian news agencies reported, citing the defence ministry.

The defence ministry said it believed the reason for the crash was equipment failure, the TASS news agency reported.

The crash occurred at 3.42pm local time during a training flight, and the helicopter was flying without weapons, news agencies cited the defence ministry as saying in a statement.

An investigation was opened to confirm the cause of the crash, which occurred in the Dzhankoi region of northern Crimea.

In a tweet, Ukrainian president Volodymyr Zelenskiy has thanked the British prime minister Rishi Sunak for the provision of long-range cruise missiles.

He said:

Had a phone call with UK prime minister Rishi Sunak. Thanked for the significant enhancement of our capabilities with long-range Storm Shadow missiles and other irreplaceable military assistance.

We discussed further defence cooperation and coordinated our positions on the eve of upcoming international events. In particular, we need clear signals about Ukraine’s future with Nato.

Yesterday, the UK defence secretary Ben Wallace confirmed that the UK would send long-range cruise missiles.

Zelenskiy is expected to attend the next Nato summit in Vilnius in July, but has repeatedly requested for a firmer time table and more concrete steps for Ukraine to join the alliance.

At a secret location in southern Ukraine, Roman Kostenko watched a drone rise into the sky. It ascended to a height of 100 metres, buzzing above a yellow rapeseed field. The drone dropped a dummy anti-tank grenade on to a pile of tyres. The test worked. That night Kostenko’s team repeated the exercise over occupied territory. Two bombs fell on a Russian armoured fighting vehicle. It blew up, smoke pluming into darkness.

Kostenko, a decorated special forces colonel, said his unit had destroyed dozens of Russian military objects. They included tanks and howitzer guns. These operations took place every night on “a tactical level”, he said, close to the frontline. This stretches for 900 miles, from the eastern city of Bakhmut where Ukrainian troops launched a local counterattack this week, to the southern provinces of Zaporizhzhia and Kherson.

There has been intense speculation that Kyiv is about to launch a major counteroffensive. On Thursday night, Russian military bloggers erroneously reported that it had already started. Speaking earlier the same day, the Ukrainian president, Volodymyr Zelenskiy, said his forces needed “some more time”. According to Kostenko, Ukraine’s long-anticipated push should be understood as a rolling “spring-summer campaign” against an entrenched and powerful adversary.

Kostenko said the campaign was already unfolding in stages. The first saw the step-by-step elimination of Russia’s military potential, with strikes against logistical targets such as weapons depots and fuel dumps. This has begun, he said. A second stage involved seeking out and eliminating Russian command and control centres, causing a breakdown of communications with troops in the field. “That’s already happening too, probably,” he said.

Ukraine’s armed forces were unlikely to embark on a major frontal offensive until they had weakened Moscow’s battlefield capability, he indicated. “Our army won’t go forward until this preparation work is done. We can’t win if they have large amounts of ammunition and resources,” he said. He acknowledged that Ukraine was playing a disinformation game about when and where it might strike, with signs that it was working, and that Moscow was beginning to panic.

• Russia’s defence ministry has denied reports that Ukrainian forces had broken through in various places along the frontlines and said the military situation was under control. Moscow was reacting after Russian military bloggers, writing on the Telegram messaging app, reported apparent Ukrainian advances north and south of the eastern Ukrainian city of Bakhmut, with some suggesting a long-awaited counteroffensive by pro-Kyiv forces had started. The Ukrainian president, Volodymyr Zelenskiy, had earlier said the offensive had yet to start.

• Turkey’s defence minister, Hulusi Akar, has said that parties to the Black Sea grain initiative are approaching an extension. Akar’s comment was released by his ministry in a statement on Friday, after talks in Istanbul.

• Ukrainian military analyst Oleksandr Musiyenko says Kyiv’s backers understand that a counteroffensive “may not result in the complete eviction of Russian troops and the definitive defeat of Russia in all occupied areas”. “We have to be ready for the war to continue into next year – or it could end this year,” Musiyenko told Ukrainian NV Radio. “It all depends on how the battles develop. We can’t guarantee how the counter-offensive will develop.”

• The Russian-imposed mayor of occupied Donetsk has reported on Telegram that one person was killed by Ukrainian shelling of the city overnight.

• The commander of Russia’s Black Sea Fleet has said its defences are being tightened amid a flurry of Ukrainian drone strikes targeting its home base, the Crimean port of Sevastopol. V-Adm Viktor Sokolov told Friday’s edition of the military newspaper Krasnaya Zvezda: “In connection with the threat of attacks by robotic surface and underwater systems, we have increased the technical defences of the fleet’s main base and of the ships’ anchorages”. Sokolov said the Black Sea Fleet, whose flagship, the cruiser Moskva, was sunk by Ukraine in April 2022, would receive four new ships in 2023.

• China’s foreign ministry has announced that its special representative of Eurasian affairs will visit Ukraine, Poland, France, Germany and Russia from Monday in what it calls “an effort to promote peace talks”,

• US President Joe Biden and Spanish prime minister Pedro Sánchez will discuss Ukraine, defence cooperation, and migration on Friday during a meeting at the White House. While Madrid agrees with Washington on the illegality of Russia’s February 2022 invasion of Ukraine, Sánchez will convey the divergent views of China and Brazil and propose giving greater weight to the views of non-Nato nations hurt by the war, a Spanish diplomatic source told Reuters.

• US Treasury secretary Janet Yellen met German finance minister Christian Lindner on Friday, to underscore the importance of working together to counter evasion of sanctions imposed on Russia over its war in Ukraine, the US Treasury has said.

• The prime ministers of Estonia, Latvia and Lithuania said on Friday they are considering speeding up a plan to disconnect the Baltic region’s electricity supply from Russia’s power grid.