World number one Ash Barty said on Wednesday she hoped authorities would approve travel for her coach Craig Tyzzer in the leadup to the Australian Open to allow her to better prepare for the home summer of tennis.

Barty on Tuesday announced her decision to forgo her French Open title defence in part due to a lack of preparation, with state border closures in Australia aimed at curbing the spread of Covid-19 having prevented Melbourne-based Tyzzer from travelling to her home base in Queensland.

"To not have him up in Queensland has been really tough," Barty said in a video released by Tennis Australia on Wednesday.

"I haven't been able to see him since March.

"It's been a tricky time for us to get ready ... but we tried to go through all the applications, tried to do all the right things but unfortunately we were rejected.

"We'll try again for pre-season and hopefully he can come up here and we can prepare as best we can for the Australian summer."

Queensland has been relatively successful in containing the coronavirus pandemic and has closed its borders to the more populous southeastern states where there are more cases.

Some media pundits have accused Queensland authorities of having double standards in Barty's case, given the state approved the entry of hundreds of Australian Football League staff and family members last month in the leadup to its playoffs.

With Barty absent from the ongoing US Open over health concerns relating to the pandemic, Alex de Minaur has flown the flag for Australia at the Grand Slam by reaching the men's quarter-finals.

"It's great for 'Demon', I'm so rapt for him," Barty said of the 21-year-old, who plays Dominic Thiem on Wednesday in New York.

"It's the level which he really, genuinely belongs."