General manager A.J. Smith told the newspaper that the Chargers sent letters to Jackson, their leading receiver in 2009, and McNeill, their starting left tackle.
Sources told the Union-Tribune that sending letters to the players only would exacerbate the situation and that both are prepared to sit out at least a portion of the 2010 season and potentially all of it.
Jackson's salary would be reduced from $3.268 million to $583,000 if he doesn't sign in the next week. McNeill's salary would drop from $3.168 million to $600,000.
Linebacker Shawne Merriman also has missed offseason workouts, but his tender ($3.269 million) is for 110 percent of his 2009 salary.