England's Rugby Football Union has expressed concerns over whether the organizers of the women's Six Nations can successfully stage the tournament amid the COVID-19 pandemic.

Several women's Six Nations fixtures were canceled last year due to the novel coronavirus outbreak, with England the only team to fulfill all their games.

No dates have been set for the start of the 2021 edition, which serves as preparation ahead of the World Cup, which will take place in New Zealand in September.

England is the only professional side in the competition — while France is semi-professional and a majority of the players from the other four nations are amateur — raising logistical challenges including testing and travel.

"I do have concerns about how well we're going to be able to get through this period," RFU head of women's performance Nicky Ponsford told the BBC.

"I'm relatively confident about how England are going to be able to deal with it, but there are different challenges in different unions."

Organizers had previously opted not to move the tournament window from February and Ponsford said that while that was the right decision, they would now need to explore other possible options.

"We will be looking over the next 10 days to see if we can get through the entire Six Nations or as much of it as we can," Ponsford said.

"It was the right thing at the time to leave the tournament where it was, but the world has changed again. It is becoming more challenging and there is a lot to put in the mix."

England are the defending champion, having clinched their 16th title last year.