The Czech president, Petr Pavel, a decorated retired general who was previously Nato’s principal military adviser, has privately warned Ukraine’s leadership against the disaster of a rushed counteroffensive.

In recent meetings in Kyiv with Ukraine’s president, Volodymyr Zelenskiy, and prime minister, Denys Shmyhal, Pavel cautioned that they no longer had the element of surprise that aided successful assaults on the eastern city of Kharkiv and southern region of Kherson last year.

The war hero, who was chair of the Nato military committee until 2018 and decorated by the Czech and French governments for rescuing French troops besieged by the Serbs during the Bosnian war in 1993, said there was recognition in Kyiv that gaps remained in Ukraine’s capacity for a successful offensive against Russian forces.

He said Zelenskiy had asked him and his Slovak counterpart, Zuzana Čaputová, for their nations each to arm a Ukrainian mechanised brigade before the long-anticipated counter-assault.

“Apparently, they still have a feeling that they do not have everything to start successfully an operation,” Pavel said.

With preparations still being made, Pavel, who was elected in January, said he had appealed to Shmyhal during meetings last week not to be “pushed into a faster pace before they are fully prepared”.

“Because it might be a temptation to push them, for some, to demonstrate some results,” Pavel said in an interview during a visit to London for King Charles’s coronation. “It will be extremely harmful to Ukraine if this counteroffensive fails, because they will not have another chance, at least not this year.”

Ukraine would inevitably face “terrible losses” no matter the strength of its forces, he said, and it could not afford for the assault to fail. “Because it’s extremely demanding in terms of putting together personnel equipment, ammunition logistics, fuel financing. It will simply be one chance this year, so it has to be successful.”

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