The NHL told its seven Canadian-based teams on Thursday that there is a possibility they will have to play in the United States this season due to roadblocks with Canadian health authorities, sources told ESPN.

The NHL had been hoping to play a 56-game season starting on Jan. 13 with teams playing in their own arenas. That plan included divisional realignment and an all-Canadian division -- necessary because the U.S.- Canada border remains closed to nonessential business. However, provincial health authorities in Canada have challenged some of the NHL's proposed protocols, which could force a change. The NHL and NHLPA were hoping to have a plan in place by the end of the week -- which would need to be approved via vote by the board of governors and the NHLPA's executive committee -- but as of Friday morning, the two sides continue to hammer away at details.

Sportsnet was the first to report about the challenges with the Canadian health authorities.

While the development has slowed some of the NHL's momentum, it isn't a big surprise: The NBA's Toronto Raptors are beginning their season in Tampa, Florida.

Sources tell ESPN that commissioner Gary Bettman has consulted with Dr. Anthony Fauci over the past few months, as well as other leading infectious disease experts, as the league formulates its strategy. The NHL and NHLPA have been meeting daily over the past two weeks.

The NHL has vowed to remain nimble as it looks to award a Stanley Cup before the Tokyo Olympics in July 2021 -- with the goal of restoring a normal cadence for the 2021-22 season. But some teams are already facing challenges due to local restrictions stemming from COVID-19.

"We have a couple of clubs that can't hold training camp or conduct games even without fans in their current buildings and facilities," Bettman told a video panel discussion hosted by the World Hockey Forum in Moscow on Thursday. "And we're going to have to move them somewhere else to play."

Sources told ESPN that the San Jose Sharks are making contingency plans to open their training camp in Scottsdale, Arizona, because of Santa Clara County's ban on contact sports (which has also forced the NFL's San Francisco 49ers to temporarily relocate operations to Arizona).

This week, dozens of NHL players voluntarily returned to their playing cities, with the expectation that the season would start on Jan. 13 and training camps would begin a few days after Christmas. The NHL and the players' association agreed to allow the seven teams that did not qualify for 2020's expanded playoff field to have additional training camp time since they hadn't played since March. But sources told ESPN that because of the time crunch, those teams might get only an additional one to three days, if anything.

If the NHL can't continue with its first option -- teams playing in their own arenas -- the league is willing to pivot to a hybrid bubble or hub city format.

"Right now, we're focused on whether or not we're going to play in our buildings and do some limited traveling or play in a bubble," Bettman said at Thursday's World Hockey Forum panel. "That's something we're working on and getting medical advice on."