Warren Buffett, chairman and CEO of Berkshire HathawayDavid A. Grogan | CNBCWarren Buffett’s Berkshire Hathaway this week added to his own already-enormous bet in Bank of America in a time once the coronavirus pandemic dampens the financial outlook and interest levels maintain close listing lows.A Securities and Exchange Commission filing revealed Buffett’s conglomerate purchased 21.2 million shares of their banking giant between Tuesday and Thursday. That raised Berkshire’s stake in Bank of America by $522 million and sets its own complete standing at the bank in 11.8%.The average buy price was $24.65 each share.Berkshire was buying small quantities of Bank of America stock daily as July 20.Last week, a comparable filing showed the Berkshire purchased 33.9 million shares of their banking giant between Monday and Wednesday. That raised Berkshire’s stake in Bank of America by $813.3 million to greater than $24 billion.In entire because the current purchasing started, Berkshire has bought $1.7 billion worth of those stock. News of Berkshire’s newest nibbles in Bank of America was not sufficient to maintain stocks from negative territory in premarket trading because of 7:30 a.m. ETdown 0.25% prior to the opening bell. Berkshire also has stakes in JPMorgan and Wells Fargo.Bank stocks are hit recently has concerns regarding the market keep interest rates low. Bank of America stocks are off by 29% this year.Though Buffett voiced his usual upbeat tone on the American economy during Berkshire’s annual shareholder’s meeting in May, he did acknowledge the extreme pressure the Covid-19 pandemic is having on certain industries.”Nothing can basically stop America,” Buffett told shareholders. “The American miracle, the American magic has always prevailed and it will do so again.”However, the Oracle of Omaha also revealed he sold out of his airline holdings due to the uncertainty caused the outbreak.— With reporting by Alex Crippen.Subscribe into CNBC PRO for exclusive insights and analysis, and reside company day programming from across the world.