The grandfather of US President-elect Donald Trump begged German authorities not to be deported from the country for failing to complete obligatory military service, the Bild newspaper reported on Monday.

In a letter from the historical archive of Germany's south-western town of Speyer, Trump's grandfather Friedrich begged Luitpold - the "well-loved, noble, wise and just" prince regent of Bavaria - not to deport him, the German newspaper reported.

Trump's grandfather grew up in Kallstadt in Germany's south-western Rhineland-Palatinate region, but left for the United States around 1885 - first to New York and later to the west as part of the Gold Rush, where he ran taverns and a brothel.

Friedrich and his wife returned to Kallstadt due to homesickness, but were forced to return to the US in 1905 over his failure to give the proper notice of departure and to complete his obligatory military service.

His "most subservient request" not to be deported was rejected by Luitpold in another letter seen by Bild. The documents were retrieved from the Speyer archive by local historian Roland Paul.