MOSCOW—Russia’s largest lender Sberbank said on Thursday that it was prepared for any developments as the threat of sanctions grew after Russian forces attacked Ukraine, sending shares in Russian banks crashing. Russian forces invaded Ukraine by land, air, and sea on Thursday, confirming the worst fears of the West with the biggest attack by one state against another in Europe since World War Two. A senior U.S. administration official told reporters on Tuesday that Sberbank and No. 2 lender VTB would face U.S. sanctions if Moscow proceeded with its invasion of Ukraine, warning that no Russian financial institutions were safe. “We are prepared for any development of the situation and have worked through scenarios for guaranteeing that our customers funds, assets and interests are protected, and also that our functions are fully operational,” Sberbank said on Thursday. VTB said its branches, ATMs, and online services were functioning normally. Both banks …