Russian and Belarusian players will not be allowed to compete at Wimbledon this year because of the invasion of Ukraine.
Men’s world number two Daniil Medvedev of Russia and women’s world number four Aryna Sabalenka of Belarus are the highest-ranked players to be affected.
The players are also banned from any of the UK grass-court tournaments.
The governing body of men’s tennis said the move was “unfair ” and could “set a damaging precedent for the game”.
In a statement the ATP said: “Discrimination based on nationality also constitutes a violation of our agreement with Wimbledon that states that player entry is based solely on ATP rankings.
“Any course of action in response to this decision will now be assessed in consultation with our board and member councils.”
Explaining its decision, the All England Lawn Tennis Club (AELTC) said it had a responsibility to “limit Russia’s global influence through the strongest means possible”.
Wimbledon runs from 27 June to 10 July.
“In the circumstances of such unjustified and unprecedented military aggression, it would be unacceptable for the Russian regime to derive any benefits from the involvement of Russian or Belarusian players,” a statement from the AELTC read.
“It is therefore our intention, with deep regret, to decline entries from Russian and Belarusian players to Wimbledon.”