Dec 17 (Reuters) - The NFL on Friday postponed games for the first time all season due to COVID-19, the NBA unveiled tighter protocols and the NHL shut down three teams through Dec. 26, further clouding their plans to send the world"s top players to the Beijing Olympics. The moves by the three leagues come as the highly contagious Omicron variant threatens to intensify an already alarming surge of COVID-19 cases in North America and also conjured memories of March 2020 when professional sports ground to a halt. The Cleveland Browns were originally scheduled to host the Las Vegas Raiders on Saturday but with two quarterbacks among their roughly 20 players on the reserve/COVID-19 list, will now play the game on Monday. The Seattle Seahawks-Los Angeles Rams and Washington Football Team-Philadelphia Eagles games that were originally scheduled to be played on Sunday will now go ahead on Tuesday. "We have made these schedule changes based on medical advice and after discussion with the NFLPA as we are seeing a new, highly transmissible form of the virus this week resulting in a substantial increase in cases across the league," the NFL said in a news release. In a memo sent to NFL teams on Friday and seen by Reuters, Commissioner Roger Goodell reiterated the league"s aim was to complete the season safely within the current 18-week schedule. The National Hockey League shut down the Calgary Flames, Colorado Avalanche and Florida Panthers through at least Dec. 26 because of COVID-19 concerns, a move that brings to 20 the total number of games postponed so far by the league this season. "A decision on when each team"s training facilities will re-open will be made by the league and the NHLPA in the coming days," the NHL said in a news release. Earlier on Friday, the NHL postponed Saturday"s game between the host Montreal Canadiens and Boston Bruins given the visiting team has seven players in the NHL"s COVID-19 protocol. OLYMPIC CONCERNS The moves by the NHL does little to quell concerns regarding the league"s plan to send the world"s top players to the Feb. 4-20 Beijing Olympics. The NHL agreed to a break in its schedule to make way for players to compete in Beijing with the caveat that it could withdraw on its own if an abundance of COVID-19 disruptions forced games to be rescheduled during the Olympic window. The Toronto Maple Leafs said on Friday that captain John Tavares, who represented Canada and won gold at the 2014 Sochi Olympics, and a team mate entered the NHL"s COVID-19 protocol and that the team"s practice has been cancelled. The NBA rolled out tighter COVID-19 protocols amid a sudden wave of COVID-19 cases and, according to a memo seen by Reuters on Friday, will increase testing from Dec. 26-Jan.8 and return to mask usage in many situations until agreed otherwise by the league and union representing its players. As per the memo, players and staff will undergo daily testing with the exception of those who are on an off day, received a booster shot 14 days prior or recently recovered after a positive or inconclusive test result. Players, regardless of vaccination or booster status, must also wear face masks while on the bench during games, travelling and in team facilities. The United States Olympic & Paralympic Committee, which in September stated that all U.S. athletes hoping to compete at the 2022 Winter Olympics would need to be vaccinated, said on Friday that Americans competing in Beijing will not be required to have COVID-19 booster shots. read more