UPDATE 1-Telefonica Deutschland willing to back German fiberco venture

(Adds detail and context on fiberco venture)

BERLIN, Oct 28 (Reuters) - Telefonica Deutschland is ready to invest some proceeds from its recent sale of towers assets into a proposed German fibre networks venture led by its Spanish parent, CEO Markus Haas said on Wednesday.

Haas said he would plough a “smaller part” of the windfall of 1.5 billion euros ($1.8 billion) from the towers sale into the venture led by Spanish parent Telefonica that he expected to be announced very soon.

Group headquarters in Madrid is assembling a 5 billion euro financing package to back the project, with banks to lend around two-thirds of the total, sources have told Reuters.

The private equity arm of German insurer Allianz is also expected to come on board as an equal partner, Spanish newspaper Expansion has reported.

Telefonica reports group results on Thursday. ($1 = 0.8461 euros) (Reporting by Douglas Busvine; editing by Thomas Seythal)