Many of the NBA's top players are expressing apprehension about accepting invitations to participate in league-sponsored Public Service Announcements to bolster broader acceptance of the coronavirus vaccine, sources told ESPN.

The NBA's outreach to the agents of many of the league's elite players -- with hopes of getting stars to participate in PSAs to promote the safety and effectiveness of the vaccine -- has been met with a tepid response, sources said. Player apprehension about receiving the vaccine are consistent with those that also exist in Black communities throughout the country, agents and players told ESPN.

Sources describe a number of factors contributing to many players' reluctance to participate, including uncertainty about taking the vaccine themselves, reluctance to advocate its use for others and resistance to extending favors to a league amid the largely unpopular plans for an All-Star Game.

On a call with league general managers on Tuesday, commissioner Adam Silver continued to tell top team executives that the league wouldn't "jump the line" of the general public to get vaccines, but he suggested an optimistic timeline that included the possibility of late March and early April for the start of player vaccinations, sources said. Nevertheless, that's considered a fluid timeline, largely meant to reaffirm to teams the need to be prepared for whenever the opportunity to vaccinate players comes from public health officials, sources said.