** Shares in 1&1 1U1.DE jump around 20% after United Internet UTDI.DE said it decided to launch an offer to take its stake in the German mobile and broadband provider to up to 90%
** United Internet, which owns 80.81% of 1&1's capital, plans to buy a further up to 9.2% stake, offering 18.5 euros per share, a 20% premium to 1&1's Thursday close
** A de-listing and squeeze out of 1&1 is not intended, United Internet said
** If gains hold, the stock will see its best day since September 2003
($1 = 0.8922 euros)
(Reporting by Marleen Kaesebier)
((marleen.kaesebier@thomsonreuters.com))