Negotiations have reached a standstill in the Buffalo Bills' bid to sign defensive tackle Marcell Dareus to a long-term contract, two people familiar with the talks told The Associated Press on Thursday.

Both people spoke on the condition of anonymity because the negotiations are private.

One person said the sides haven't exchanged offers in a few weeks, raising concerns that a deal won't be completed before the start of the season in three weeks. The season opener is not considered a hard deadline.

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The 25-year-old Dareus will make just over $8 million in the final year of his contract this season. Earlier this week, Bills general manager Doug Whaley had no update on the talks, but added "these take time."

Selected with the third pick in the 2011 draft out of Alabama, Dareus has been a four-year starter and established himself as one of the NFL's top young defensive linemen. He's a two-time Pro Bowl selection and earned his first All-Pro honor last season, when he led the league's defensive tackles with a career-best 10 sacks.

Dareus has been part of an aggressive defense that has combined for an NFL-leading 111 sacks over the past two seasons.

The Bills have already committed a large portion of their payroll toward the defensive line. Defensive end Mario Williams is set to make a $12.1 million base salary this season -- the fourth of the player's six-year, $100 million deal. In March, the Bills re-signed defensive end/linebacker Jerry Hughes to a five-year, $45 million contract.