European rugby chiefs are hoping for a modification of French quarantine rules that could threaten several Heineken Champions Cup and Challenge Cup fixtures this weekend.
Munster take on Castres on Friday evening, however as Ireland is on the French green list the new entry restrictions will not apply to Johann van Graan's side.
The rules imposed on UK travellers - which include a requirement to self-isolate for at least 48 hours after entering France - threatened to impact several matches in the final two rounds of the pool phase.
Bath, Sale and the Scarlets are due to play European Cup games in France against La Rochelle, Clermont Auvergne and Bordeaux-Begles respectively on Saturday and Sunday.
Newcastle, meanwhile, are scheduled to visit Challenge Cup opponents Biarritz on Friday.
European Professional Club Rugby (EPCR), organiser of both tournaments, said last week the competitions would continue as planned for the remainder of the pool stage after it was confirmed clubs and match officials would be granted exemptions from French travel restrictions.
EPCR has been told that exemptions for what is termed the "pursuit of an economic activity" applies to players, coaching staff and officials taking part in the European Cup and Challenge Cup.
Clubs travelling to France, though, are concerned about the quarantine rule, which requires negative Covid-19 tests to leave isolation. Any positive PCR or antigen test would lead to a longer quarantine period in the country.
EPCR remain in dialogue with France's Ligue Nationale de Rugby, which oversees the country's professional game, and the PA news agency understands there is hope for a modification of existing quarantine requirements.
To comply with current rules, Newcastle would need to arrive in France on Wednesday, while they also have a Challenge Cup fixture away against Toulon next week.
EPCR must also find a window in the packed rugby calendar to re-stage round two matches that were called off before Christmas because of French travel restrictions.
Rather than issue a 28-0 defeat to one team, as happened to Leinster when they suffered an outbreak of coronavirus, it was decided to find a new date for games that fell victim to the safety measures brought in at short notice.