Milan would rather keep Ronaldinho until the summer than pay him a lump sum to terminate his contract in January.
It's understood that Brazilian club Gremio have already agreed personal terms with the attacking midfielder who has spent most of this season on the bench in Serie A.
However, the proposed New Year switch can only go through if Milan and Ronaldinho can agree terms over a rescission.
Some reports in Italy on Friday are suggesting that talks have begun, but there is a difference of opinion.
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