Former 400m hurdles world champion Dai Greene says his hopes of qualifying for Tokyo 2020 are "getting slimmer" by the day because travel restrictions mean he cannot get to competitions.
The Welshman said he has a "general feeling of helplessness" as chances to race are "very thin on the ground".
The delayed Olympics begin on 23 July.
Greene, 35, added it is a bit "hollow" for the International Olympic Committee (IOC) and the organisers in Japan to be proceeding with the Games.
In the past few weeks Greene has had to pull out of competitions in France and Switzerland because of self-isolation requirements, and one in Sweden as he was unable to get a PCR test in time.
It means his last two opportunities to achieve the qualifying standard for Tokyo are in Denmark next week and the British Championships at the end of the month.
"It's very thin on the ground in terms of competitions," he told BBC Sport.
"It's very difficult at the moment for athletes to get that level of competition they need to get exposure to faster races, better environments, faster tracks to get the harder qualifying times that have been put on us at the moment.
"In the next three weeks I have to run just as fast as the athletes ran to make the World Championship final in 2019. It's a very difficult ask and I'm not the only one in this situation.
"If I'm being totally honest my chances are getting slimmer all the time."
Greene said the Tokyo 2020 Olympics will be his last. He has been involved in athletics for 16 years and won world gold in Daegu in 2011.
But his preparations have been so complex he says it has been the most stressful month of his career.
"It's a general feeling of helplessness that I can't even get the opportunity to fully have a season or have a stab at the standard," he said.
"It's a really frustrating time for athletes and we're running out of time. There isn't the domestic competition on to make up for the loss of access to those abroad.
"It's pretty much all we are talking about now as athletes."
There are now fewer than 50 days to go until Tokyo 2020. Earlier this week Seiko Hashimoto, president of the organising committee, told the BBC that the Games are 100% going ahead.
Japan is currently experiencing a fourth wave of coronavirus, but Hashimoto said she is confident no firmer measures could be being taken to make the event safe and secure.
However, Greene is not convinced the Games are taking place for the right reasons.
"I feel as though it's a bit of a hollow thing to put it on this year in comparison to past Games," he said.
"It's going ahead for the sake of it going ahead more so than a celebration of the sport."
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