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Associated Press
San Francisco 49ers quarterback Alex Smith (11) passes against the New Orleans Saints in an NFL divisional playoff football game Saturday, Jan. 14, 2012, in San Francisco. (AP Photo/Ben Margot)

SAN FRANCISCO — A person with knowledge of the negotiations says Alex Smith and the San Francisco 49ers are working to finalize a three-year contract.

NFL Network first reported the sides had agreed on a new deal. The person, speaking on condition of anonymity because no announcement had been made, said Tuesday night final details are still being worked out and an announcement could come as soon as Wednesday.

Earlier in the day, Peyton Manning was formally introduced in Denver after the 49ers pursued the four-time NFL MVP.

The 27-year-old Smith had met with Miami on Sunday but ultimately decided to stay put with the team that drafted him first overall in 2005.

Smith had a breakthrough season last year, helping San Francisco reach the NFC title game.