Wimbledon's decision to ban Russian and Belarusian players from this year's tournament has been slammed as "unfair" by men's tour organisers the ATP.
All England Club chiefs on Wednesday revealed their move in response to Russia's invasion of Ukraine.
But ATP bosses claim the ban, which extends to all Lawn Tennis Association events in Britain, is discriminatory and sets a damaging precedent.
Russian and Belarusian players had been allowed to compete in ATP tournaments since the war in Ukraine started, although they were not able to use their national flags.
The ITF had already banned both countries' teams from the Davis Cup and the Billie Jean King Cup.
"We believe that today's unilateral decision by Wimbledon and the LTA to exclude players from Russia and Belarus from this year's British grass-court swing is unfair and has the potential to set a damaging precedent for the game," an ATP statement 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.
"We strongly condemn Russia's reprehensible invasion of Ukraine and stand in solidarity with the millions of innocent people affected by the ongoing war.
"Our sport is proud to operate on the fundamental principles of merit and fairness, where players compete as individuals to earn their place in tournaments based on the ATP Rankings."
Russian men's world number two Daniil Medvedev is the top player from both countries to be affected by the Wimbledon ban.
At present, the ATP insists they have no plans to change their stance on allowing Russians and Belarusians to take part in their tournaments.
"It is important to stress that players from Russia and Belarus will continue to be allowed to compete at ATP events under a neutral flag, a position that has until now been shared across professional tennis," the statement said.
"In parallel, we will continue our joint humanitarian support for Ukraine under Tennis Plays for Peace."
Pledging to consider a further response to the Wimbledon ban, the ATP said: "Any course of action in response to this decision will now be assessed in consultation with our Board and Member councils."