MILAN, Jan 8 (Reuters) - KKR plans to notify the European Union's antitrust authorities by the end of January of its planned buyout of Telecom Italia's (TIM) fixed access network, two sources close to the matter said on Monday.

Italy's former phone monopoly agreed in November to sell its prized landline grid to the U.S. fund in a deal worth up to 22 billion euros ($24 billion) which is aimed at significantly reducing TIM's debt and staff.

While supported by the Italian government, which plans to take a 20% stake in the network company to oversee an asset deemed of strategic national importance, the deal is being challenged in court by top TIM investor Vivendi.

TIM expects to finalise the deal, which requires EU antitrust approval, by the summer.

The sources said KKR had already started informal talks with EU antitrust authorities ahead of a formal notification, which is expected by the end of January.

KKR declined to comment. The EU Commission did not immediately respond to a Reuters request of comment. ($1 = 0.9115 euros) (Reporting by Elvira Pollina; Editing by Alexander Smith)