Dec 17 (Reuters) - The National Football League has postponed games for the first time all season due to COVID-19 outbreaks that required three upcoming contests to be rescheduled from the weekend to early next week, the league said on Friday. The Cleveland Browns, who were set to face the Las Vegas Raiders in a Week 15 encounter on Saturday, will now host the game on Monday, the NFL said in a news release. 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. The decision by the NFL, which discussed the moves with the NFL Players Association, comes as the highly contagious Omicron variant threatens to intensify an already alarming surge of COVID-19 cases in North America. "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. Cleveland, who are one game out of first place in the AFC North division, have placed about 20 players, including both of their quarterbacks, on the reserve/COVID-19 list this week. The explosion of positive tests indicates the NFL could be feeling in the impact of the Omicron variant. Early evidence suggests that Omicron is spreading faster than its predecessor, Delta, and is more likely to infect people who were vaccinated or had COVID in the past. "Although we are unable to disclose specifics, we are fortunate that every member of our organization who has recently tested positive was vaccinated, the majority of which are currently asymptomatic or experiencing mild symptoms," the Browns said in a statement. Former Super Bowl Most Valuable Player Von Miller was one of nine Rams added to the reserve/COVID-19 list on Thursday, according to the NFL website, with a total of 25 players from the franchise on the list. Washington quarterback Taylor Heinicke was placed on the list on Friday amid reports that the team now has over 20 players on the list overall.