Pro Bowl running back Jamaal Charles has reached a two-year contract extension with the Kansas City Chiefs.

The deal will keep Charles in Kansas City through the 2017 season, a person familiar with the contract said Wednesday on condition of anonymity because the team has not disclosed details. He is now expected to take part in the first practice scheduled for Thursday.

"I had no intention on holding out," Charles tweeted. "I just ran out of gas on the way to camp and my cellphone battery died. It was a long walk I tell ya."

The six-year NFL veteran ran for 1,287 yards and 12 touchdowns last year as the Chiefs reached the playoffs. He also had 70 catches for 693 yards and seven more TDs as Kansas City went 11-5 before losing to Indianapolis in an AFC wild-card game.

Charles comes off a season with career highs in yards from scrimmage (1,980), rushing touchdowns, total touchdowns, receptions, receiving yards and receiving touchdowns.

Charles' earned a base salary of $1.75 million in 2013, according to NFLPA records. He was set to earn a base salary of $2.65 million, which ranked 11th among NFL running backs, before the contract extension. Various media reports, including from NFL.com and ESPN, put Charles' two-year extension at $18 million.

With Charles secured through 2017, the Chiefs can shift focus to quarterback Alex Smith and outside linebacker Justin Houston, both of whom enter the final years of respective contracts.

Smith, 30, comes off a season where he completed 308-of-508 passes for 3,313 yards and 23 touchdowns against 13 interceptions.

- Associated Press