Dhaka, July 22 -- Japanese premier Shigeru Ishiba vowed to stay on after his ruling coalition suffered a bruising defeat in upper house elections on Sunday as some of his own party discussed his future and the opposition weighed a no-confidence motion.In a series of televised remarks as the results came in on Sunday evening, Ishiba told reporters he would remain as prime minister, citing a looming tariff deadline with the United States set to strain the world's fourth largest economy.Ishiba is due to hold a press conference at 2pm (0500 GMT) where he will formally announce those plans, broadcaster NHK reported.Analysts say his days may be numbered, having also lost control of the more powerful lower house in elections last year and sheddi...