It comes after the Foreign Office warned of cross-sector demonstrations over 7-11 February, which it said could disrupt travel services.
Schools in England will break up on Friday 10 February. Eurostar said its decision was precautionary, adding it would provide updates regarding any timetable changes.
Advantage Travel Partnership chief Julia Lo Bue-Said on Friday (3 February) separately warned of the potential impact for families and skiers of a strike by Border Force officials over 17-20 February at four ports – Dover, Calais, Coquelles and Dunkirk.
"We’re aware of planned strike action in France on Tuesday 7 February, Wednesday 8 February and Saturday 11 February," said Eurostar in a travel alert on its website.
"While we assess the impact on our timetable, as a precautionary measure, we’ve closed sales on all trains leaving from London on 11 February.
"As soon as we have confirmed information to share, we will update this page and contact passengers if their Eurostar journey is affected by timetable changes."
