Wimbledon was left with "no viable alternative" to banning Russian and Belarusian players from this year's Championships, tournament chiefs at the All England Club said on Tuesday.
Organisers of the Grand Slam last week announced the move in response to Russia's invasion of Ukraine, meaning stars such as Daniil Medvedev, Andrey Rublev, Aryna Sabalenka and Victoria Azarenka cannot play at the event, which starts in late June.
The decision was criticised by the ATP, which runs the men's tour, and women's tour organisers the WTA, while Rublev labelled it "complete discrimination" and defending Wimbledon champion Novak Djokovic said it was "crazy".
But All England Club (AELTC) chairman Ian Hewitt defended the move, saying the decision was made after careful consideration, taking into account UK government guidance.
"We have considered at length the options available," he told reporters.
"These are in effect two options -- declining entries or allowing entries but only with specific declarations (against the invasion of Ukraine) from individual players.
"We considered a wide variety of factors. After lengthy and careful consideration, we came to two firm conclusions.
"First, even if we were to accept entries (from Russian and Belarusian players) with written declarations, we would risk their success or participation being used to benefit the propaganda machine of the Russian regime, which we could not accept.
"Second, we have a duty to ensure no actions should put players or their families at risk. We understand and deeply regret the impact this will have on all the people affected.
"We believe we have made the most responsible decision possible. We believe (given government guidance) there is no viable alternative in this truly exceptional and tragic situation."
- Downgrade? -
As the Grand Slam tournaments are autonomous, possible sanctions by the ATP and the WTA could include a refusal to award ranking points at the event, which runs from June 27 to July 10.
That could reduce Wimbledon to the status of a high-profile exhibition event.
Players representing Russia and Belarus are currently allowed to take part in ATP and WTA events but are barred from competing under the name or flag of their countries.
Their national teams have, however, been banished from the Davis Cup and BJK Cup competitions.
AELTC chief executive Sally Bolton said officials were in daily communication with the tours, adding: "We won't be speculating on what may or may not happen in the future.
"We continue to make the case for why we have made the decision we have made and the unique set of circumstances we find ourselves in here in the UK. They absolutely appreciate that."
Bolton also revealed that discussions are ongoing with the British government regarding Russian coaches and other officials, while Russian media outlets will also be banned.