KANSAS CITY, Mo. — Ever since negotiations for a long-term contract broke off last year, Jared Allen's departure from the Chiefs carried a sense of inevitability.

It came true tonight when the Chiefs agreed to trade their Pro Bowl defensive end to the Minnesota Vikings, a source said.

The Chiefs and Vikings had discussed a deal earlier in the day that would send Minnesota's first- and both of the Vikings' third-round picks to Kansas City. It's unclear whether the deal had changed by the time it had been agreed upon.

The teams had also discussed swapping picks in a later round.

Allen also agreed to terms on a contract with the Vikings and was en route to Minnesota today to sign the deal. Terms of the contract were unavailable.

Allen was an unheralded fourth-round draft pick from tiny Idaho State when he joined the Chiefs in 2004. He quickly established himself as one of the Chiefs' best defensive players and last season emerged as a dominant player. He led the NFL in sacks with 15› in just 14 games.

Allen and the Chiefs found themselves at odds last year over negotiations for a long-term contract. The Chiefs were fearful of giving Allen such a lucrative deal after he had been arrested twice in Johnson County for DUI. He served a two-game suspension last season for violating the league's substance-abuse policy.

Allen believed the Chiefs reneged on promises to sign him to a long-term deal. In February, the Chiefs designated him as their franchise player.

But recently the Chiefs began fielding calls inquiring about a trade. Allen met with the Vikings in Minnesota over the weekend .

The move could change the Chiefs' draft strategy this weekend. Losing Allen could mean the Chiefs switch to defense with their No. 5 pick of the draft.