President of Ukraine Volodymyr Zelensky has acknowledged battlefield progress has been "slower than desired", weeks into Ukraine's military offensive to recapture areas occupied by Russia.
"Some people believe this is a Hollywood movie and expect results now. It's not," he told the BBC.
"What's at stake is people's lives."
Ukraine says its counter-offensive has reclaimed eight villages so far in the southern region of Zaporizhzhia and Donetsk to the east.
Zelensky said the military push was not going easily because 200,000 sq km (77,220 sq miles) of Ukrainian territory had been mined by Russian forces.
"Whatever some might want, including attempts to pressure us, with all due respect, we will advance on the battlefield the way we deem best," Zelensky added.
He reinforced the need for Ukraine to be given security guarantees from Nato but said ultimately the goal was membership of the defensive alliance.
Nato's secretary-general made clear this week that no plan was on the table to issue an invitation to Ukraine at next month's summit in Lithuania.
"[Jens] Stoltenberg knows my position," the Ukrainian leader said. "We've told them numerous times: 'Don't knock the ground from under our feet.'"
The Ukrainian leader again made the case for Ukraine to receive US-made F-16s and said he believed fighter pilots could start training as soon as August, and that the first jets could arrive in six or seven months' time.
Zelensky was speaking to the BBC to mark a Ukraine Recovery Conference in London focusing on the role the private sector can play in rebuilding his country. He later spoke at the conference, along with UK PM Rishi Sunak.
Ukraine's economy shrank by 29.2% in 2022 and earlier this year the World Bank estimated the cost of reconstruction and recovery at $411bn (£339bn).
The Ukrainian leader told the BBC that the support he needed was not just for recovery but for transformation as well.
He said "quick steps" to be done immediately included finding places for people to live, rebuilding the destroyed Kakhovka dam and decentralising the energy network.
"But on the larger scale we are speaking about the transformation of Ukraine," he explained. "This is Ukraine not only with its energy and agriculture and industrial complexes, but with its reforms we can see."
He spoke of "the digitilization of Ukraine" as well as judicial and anti-corruption reforms.
When asked what the endgame of the war looked like at this stage, he made clear that "victories on the battlefield are necessary" and that Ukraine would never sit down, whoever was president in Moscow, if Russia remained on Ukraine's territory.
"No matter how far we advance in our counter-offensive, we will not agree to a frozen conflict because that is war, that is a prospectless development for Ukraine."
Russia announced a few days ago that it had moved tactical nuclear weapons to Belarus and President Joe Biden has warned that the threat of Vladimir Putin using them is real.
