TOKYO—Japanese financial conglomerate SBI Holdings said on Friday it would extend the deadline for its $1.1 billion unsolicited tender offer for Shinsei Bank to Nov. 24 from Oct. 25 if Shinsei agreed to meet certain conditions. SBI, which owns Japan’s largest online brokerage, operates an online bank and has stakes in multiple regional banks. It is planning to increase its stake in Shinsei to as much as 48 percent from 20 percent to take effective control of the lender. Struggling to find ways to thwart the takeover, Shinsei said last week if its board decided that SBI’s bid would damage its corporate value, it would seek shareholder approval on an undecided date to issue stock warrants to existing shareholders, a measure that would dilute SBI’s stake. It was also requesting a deadline extension for the tender offer to Dec. 8. In a letter that was released publicly responding to Shinsei’s …