STATE'S SECRETS; Cables Mostly Laud French Friend With 'Mercurial' Side.

PARIS -- President Nicolas Sarkozy is an unusually solid French friend of America. He is also a ''mercurial'' man operating in ''a zone of monarch-like impunity'' surrounded by advisers often too fearful to give honest counsel, according to leaked cables from the United States Embassy in Paris. Last December, the American ambassador shared an anecdote with Secretary of State Hillary Rodham Clinton: when the mayor of Paris had the Eiffel Tower lighted in Turkey's national colors for a visit by Prime Minister Recep Tayyip Erdogan in April 2009, aides to Mr. Sarkozy, a staunch opponent of Turkey's entry to the European Union, rerouted the presidential plane so he would not see it. [ABSTRACT FROM AUTHOR]