Oct 21 (Reuters) - Western Digital Corp"s (WDC.O) talks to merge with Japanese chipmaker and partner Kioxia Holdings Corp have stalled over the last few weeks, two people familiar with the matter told Reuters on Thursday. The talks reached a standstill over concerns about the valuation, approval from the Japanese government and an ongoing strategic review at Kioxia shareholder Toshiba Corp (6502.T), the sources said. Earlier in August, Reuters reported that Western Digital was in advanced talks for a possible $20 billion stock merger with Kioxia, in a move that would create a NAND memory giant to rival Samsung Electronics (005930.KS). read more Kioxia, sold by Toshiba Corp (6502.T) in 2018 to a consortium led by Bain Capital, shelved plans for an initial public offering last year after U.S.-China trade tensions slammed Huawei, one of Kioxia"s biggest clients. The Japanese chipmaker has said it is still considering an IPO. read more The Wall Street Journal first reported the news earlier in the day.