Harrington confirmed that he and United States captain Steve Stricker had agreed to the contingency plan that can be used alongside the usual injury envelope.

Under the new COVID-19 rule, each captain will be asked to put the names of three players in an envelope before the 12 singles matches at Whistling Straits in Wisconsin in the United States.

The envelope will only be opened if a player is forced to withdraw after testing positive with coronavirus.

"Just like an injury name in the envelope, there's a COVID name in the envelope," Harrington said.

"While we've asked, it's still not completely clear what happens if, God forbid, we had a COVID outbreak of a number of players, but for one player it's pretty straightforward.

"Obviously on Sunday, you start losing a few players to COVID, it does affect the match in some way.

"But one is in a COVID envelope for sure.

"It's the exact same as an injury envelope. 

"The person that goes in the envelope, the captain decides, and nobody ever knows.

"We hope that stays that way.

"But we've had a few injury pull-outs over the year, so it would be just very similar to that.

"No real difference in how it works."

The Ryder Cup was moved from 2020 to 2021 because of the coronavirus pandemic.

Stricker said measures to combat COVID-19 remained a top priority within the US squad.

"We're doing the sensible things," said Stricker.

"We're doing the proper things to stay safe within our team zone and within that bubble.

"Just trying to make sure that no one gets sick.

"We want to play.

"We don't want anything to jeopardise the health of any of our players or captains.

"We're paying attention to that and we're trying to do the right things."

Whistling Straits is scheduled to stage the Ryder Cup from Friday (September 24) to Sunday (September 26).