The former Hearts captain is understood to have preferred Celtic because of their likely involvement in Europe next season, though his appearances for Hearts in this year's UEFA Champions League qualifiers have made him ineligible for Celtic's current campaign.
Celtic are bringing Pressley in to shore up a defence that has been deprived of Dianbobo Balde, who has suffered a broken leg. Pressley is a free agent after agreeing to leave Hearts following his criticism of majority shareholder Vladimir Romanov.
The 33-year-old underwent a medical at Charlton but eventually opted to stay in his native Scotland. He has signed a deal until May 2008 but will not be free to make his debut for Celtic until the January transfer window officially opens and his registration can be completed. Pressley, who also had spells with Rangers FC and Dundee United FC, played alongside Celtic manager Gordon Strachan at Coventry City FC in the mid-1990s.
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