The Ukrainian president, Volodymyr Zelenskiy, has said he expects Russia to step up its offensive in the north-east and warned Kyiv has only a quarter of the air defences it needs to hold the front line. Russian forces, which had made only moderate advances in recent months, launched a surprise assault in Kharkiv region on 10 May that has resulted in their biggest territorial gains in a year-and-a-half. Zelenskiy said Russian troops advanced between five to 10km (3-6 miles) along the north-eastern border before being stopped by Ukrainian forces, but added that fighting in the region could be the “first wave” in a wider offensive. “I won’t say it’s a great success [for Russia] but we have to be sober and understand that they are going deeper into our territory,” he said, speaking to Agence-France Presse from Kyiv in his first interview with foreign media since the offensive began. Zelenskiy said the situation in the Kharkiv region had been “controlled” but “not stabilised”. He doubled down on pleas for allies to send more air defence and fighter jets to combat Russia’s air superiority as the war grinds through its third year. “Today, we have about 25% of what we need to defend Ukraine. I’m talking about air defence,” he said. He said Ukraine needed “120 to 130” F-16 fighter jets or other advanced aircraft to achieve “parity” with Russia. The president acknowledged there were issues with staffing and “morale” within Ukraine’s often outgunned and outmanned ranks. “We need to staff the reserves, he said. “A large number of [brigades] are empty.” With no end to the war in sight, Ukraine’s army is struggling to recruit, while fighters are growing exhausted and angry at the lack of rotation. Many Ukrainian soldiers have been fighting for more than two years without the possibility of being discharged. Under a controversial mobilisation law that comes into force on Saturday, Kyiv has lowered the age at which men can be drafted from 27 to 25 and tightened punishments for those who avoid being called up. However, authorities scrapped a proposal to grant soldiers who have served for more than 36 months the option to be discharged. Zelenskiy insisted Ukraine was still playing the long game as western allies pressed for a quick end to the war. “The west wants the war to end. Period. As soon as possible. And, for them, this is a fair peace,” he said. “We are in a nonsense situation where the west is afraid that Russia will lose the war. And it does not want Ukraine to lose it,” he said. The Russian president, Vladimir Putin, said during a trip to China this week the north-eastern offensive was in retaliation for Ukraine’s shelling of border regions and that Moscow was trying to create a “security zone”. Russian forces have taken 278 sq km (107 sq miles) between 9 and 15 May, their biggest gains since the end of 2022, AFP calculated using data from the Institute for the Study of War. On Saturday, the governor of Kharkiv, Oleg Synegubov, said Ukraine’s armed forces had repelled two attempts to break through defences overnight, with the situation “under control”. Ukrainian officials have accused Russian soldiers in Vovchansk of capturing dozens of civilians and using them as “human shields” to defend their command headquarters – a claim AFP was not able to immediately verify. “In the area of the city of Vovchansk, Ukrainian troops are reinforcing their defence to improve the tactical situation,” Synegubov said. Ukraine has evacuated almost 10,000 people from the north-east border area since Russia launched the assault. Putin said there was no intention at this stage to take Kharkiv, Ukraine’s second city, about 30km (18 miles) from the border. More than 1 million people still live there. Military analysts say the north-eastern offensive could aim to further stretch Ukrainian troops and resources, with Russia pressing its manpower and ammunition advantage. The Ukrainian army chief, Oleksandr Syrsky, said Russia was trying to force Ukraine to pull up even more troops from its reserves. “We realise that there will be heavy fighting ahead and the enemy is preparing for it,” he said.