Comcast Chief Executive Brian Roberts said Wednesday the nation's largest cable provider and owner of NBCUniversal has committed $500 million to support employees as coronavirus quarantines temporarily shut down business units.

In an email to employees, Roberts said Comcast would put aside that amount for pay and benefits for employees "where operations have been paused or impacted." He also said he would join Comcast's senior executives — Chief Financial Officer Mike Cavanagh, Comcast Cable CEO Dave Watson, NBCUniversal CEO Jeff Shell and Sky CEO Jeremy Darroch — in donating 100% of their salaries to charities to support coronavirus relief efforts.

Comcast has seen its broadband usage spike as Americans largely stay at home during COVID-19 quarantines. Roberts said Comcast and Sky engineers, technicians and call center representatives continue to work to keep networks running. NBCUniversal and Sky news networks have also continued to work to inform the public, he added.

Comcast's internet business positions the company in a stronger position than other media companies that are more reliant on advertising revenue and traditional pay-TV subscriptions, both of which could be weak if the nation plunges into a significant downturn, as some analysts predict. Digital media companies including Vice, Buzzfeed and Group Nine have already announced layoffs or pay cuts for their workforces.

Still, Comcast has felt operational effects from the downturn, including weathering a likely downturn in global advertising spending and temporarily shutting down its Universal theme parks. Like most media companies, Comcast has warned investors quarantines may have a "material adverse impact on our results of operations over the near to medium term." The 2020 Summer Olympics has been postponed a year, and that will impact NBCUniversal's annual revenue. The cable programmer is the sole provider of broadcast rights for the games.

"None of us has ever experienced anything like this before, and while it is easy to get mired in the many challenges we are all facing, I think that in uncertain times like these it is incumbent upon us to remain optimistic and look for the good, even if it can be elusive," Roberts said in the email, adding he didn't "know when the worst will be behind us."

Comcast shares are down about 24% this year. The S&P 500 is down about 20% over the same period.

Disclosure: Comcast is the owner of NBCUniversal, parent company of CNBC and CNBC.com.

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