The beleaguered golfer is said to have hired a lawyer specialising in international child custody arrangements.
It is thought that Miss Nordegren would move back to her native Sweden, where she has been renovating a house, and proceedings could then be filed there.
The central issue in any divorce would be the custody of the couple's two children and lawyers are said to be making arrangements to ensure both parents would have access to Sam (3) and Charlie, 14 months.
Miss Nordegren, a former swimwear model, could receive up to US$300m (£200m) in a settlement. Talk of divorce has been limited to speculation. No legal papers have been filed.