Colin Kaepernick at 49ers' facility amid trade talks with Broncos

Kaepernick has ability to pressure 49ers for trade (1:32)

John Clayton breaks down the leverage 49ers QB Colin Kaepernick has to get San Francisco to trade him to the Broncos, as well as how long he sees this process taking. (1:32)

Quarterback Colin Kaepernick was in attendance Monday for the start of the San Francisco 49ers' offseason program under new coach Chip Kelly, a source told ESPN's Adam Schefter.

Kaepernick has a $400,000 offseason workout bonus for 90 percent attendance in the workout program, which is voluntary. San Francisco and Denver have the parameters of an agreement in principle on a trade for Kaepernick, sources told Schefter, but the deal is being held up over disagreement over who will pay the quarterback's $11.9 million guaranteed salary for the upcoming season.

Monday was the first day under NFL rules that Kelly was allowed to talk football with Kaepernick and give him an iPad with the team's playbook on it.

Kaepernick's presence at the 49ers' facility was first reported by CSN Bay Area.

The Broncos are willing to pay $7 million, a source confirmed to ESPN. But Denver and Kaepernick would like San Francisco to pay the remaining $4.9 million; the 49ers have been unwilling, according to a source, contending that they should not have to pay for a player they'd like to keep on their roster. Kaepernick has also been unwilling to forfeit the $4.9 million to make the deal work, according to a source.

Kaepernick and Broncos executive vice president of football operations/general manager John Elway have met twice, as the San Francisco Chronicle previously reported. Kaepernick and Denver have made progress on the other years in the quarterback's contract, which runs through 2020, leaving the 2016 season as the only obstacle, according to a source.

Denver, which lost Peyton Manning to retirement and Brock Osweiler to the Houston Texans in free agency, has long been linked to Kaepernick and has reportedly envisioned him competing with the recently acquired Mark Sanchez.