LONDON—Finance minister Rishi Sunak says he won’t rush to fix the United Kingdom’s public finances as he readies a budget plan that will pile more borrowing on top of almost 300 billion pounds ($418 billion) of COVID-19 spending and tax cuts. Sunak, who is due to deliver his budget to parliament on March 3, promised to help the UK economy through a gradual lifting of lockdown measures that will last at least until late June. But he also said he would “level with people” about how Britain’s 2.1 trillion-pound debt pile would continue to grow without action. “This is not something that’s going to happen overnight. Given the scale of the shock we’ve experienced, the scale of the damage, this is going to take time to fix,” Sunak told Sky News on Feb. 28. “But it’s important … to also have strong public finances over time.” Sunak declined to comment …