* France's Macron requested meeting with Abe at G20 - Mainichi
* Japan minister sent France rare letter of protest - paper
* Authorities approve extension of Ghosn's detention - media (Recasts top with media reports on extension of Ghosn's detention)
TOKYO, Nov 30 (Reuters) - Tokyo authorities extended the detention on Friday of ousted Nissan Motor Co chairman Carlos Ghosn for 10 days, media said, amid signs of a brewing diplomatic feud over the balance of power at the troubled Renault-Nissan alliance.
The 19-year partnership between Renault SA and Nissan is facing its biggest test to date after the arrest this month of Ghosn, its larger-than-life leader, for suspected financial misconduct.
France said President Emmanuel Macron will meet Japanese Prime Minister Shinzo Abe on the sidelines of the G20 summit meeting that starts in Buenos Aires on Friday but did not say whether Ghosn's arrest or the auto alliance would be discussed.
Ghosn, 64, has been detained in Tokyo since his Nov. 19 arrest, and authorities on Friday approved the maximum 10-day extension of his detention, Japanese media said. Authorities have to file charges by Dec. 10 or arrest him on suspicion of fresh crimes to keep him in custody.
Tokyo prosecutors declined to comment. Nissan did not immediately respond to a request for comment.
Ghosn's detention in Tokyo has left the Franco-Japanese auto alliance without a leader and an advocate for the French government, which has said it wants to retain the current capital structure. Renault controls Nissan through its 43 percent stake, while Nissan holds a non-voting 15 percent stake in its partner.
After meeting in Paris last week, Japanese Industry Minister Hiroshige Seko and French Finance and Economy Minister Bruno Le Maire reaffirmed the two countries' support for the alliance.
A few days later, however, Le Maire said on French television that he and Seko agreed that keeping the alliance's current capital structure was desirable - an agreement the Japanese minister denied making.
The Mainichi Shimbun daily reported on Friday that Seko had sent a rare letter of protest to Le Maire for the remarks.
Officials at Japan's Ministry of Economy, Trade and Industry said they could not immediately comment on the reported letter. A French finance ministry official said Le Maires office had no comment.
Ghosn's arrest, including for allegedly under-reporting his income, has triggered new attempts by Nissan to shake off what it considers Renault's outsized control of it, adding to problems at Macron's Elysee.
As economy minister, Macron had masterminded the French government's surprise increase of its Renault stake in 2015, raising alarm bells inside Nissan that the Elysee was out to wield more influence over the Japanese company.
Macron has requested a meeting with Abe at the G20 summit starting on Friday, the Mainichi reported. A Japanese government spokesman said nothing had been decided.
The auto alliance, which also includes Japan's Mitsubishi Motors Corp, for its part "emphatically reiterated" its commitment to the partnership on Thursday after executives met in Amsterdam for the first time since Ghosn's arrest.
A review of the capital structure was not discussed at the meeting, Mitsubishi Motors' CEO Osamu Masuko said. (Reporting by Kaori Kaneko, Chris Gallagher and Linda Sieg and Elaine Lies; Additional reporting by Laurence Frost in PARIS; Writing by Chang-Ran Kim; Editing by Muralikumar Anantharaman)