LONDON, Sept 28 (Reuters) - Talks between Vodafone and Liberty Global collapsed because the two companies could not agree on the valuation of assets on either side, but the door has not closed on potential future discussions, according to a person close to the talks.

The asset-swap discussions centred on "Liberty's German cable assets and cable assets elsewhere in Europe", the source said.

Liberty owns Germany's second largest cable firm, Unitymedia, while Vodafone bought its bigger rival Kabel Deutschland in 2013.

(Reporting by Paul Sandle; Editing by Martinne Geller and David Holmes)