The Washington Nationals and first baseman Adam LaRoche ended their offseason-long stalemate Tuesday and agreed to terms on a two-year contract, returning one of their most valuable players from 2012 to the middle of their lineup while making popular slugger Michael Morse near-certain trade bait.

LaRoche, a reigning Gold Glove and Silver Slugger winner in the National League, accepted the two-year offer the Nationals had on the table since the late fall. He had been holding out for a three-year deal, but he could not find one in a market stifled by the draft-pick compensation attached to him.

“I think we both were getting tired of the process,” General Manager Mike Rizzo said. “Adam and I had a few private conversations with each other. I made it clear to Adam, ‘It’s time to get this thing done, make a decision.’ He agreed.”

LaRoche’s signing figures to push the Nationals’ 2013 opening-day payroll past $100 million, the highest it has been in franchise history. According to a person with knowledge of the deal, which LaRoche signed after passing a physical Tuesday, he will earn at least $24 million over two years. He will make $10 million in 2013 and $12 million in 2014. The contract includes a mutual option for a third year worth $15 million. If the option is not picked up, LaRoche will receive a $2 million buyout.

LaRoche’s return answers the biggest remaining question of the Nationals’ winter. He will provide another left-handed slugger in the middle of the order and allow for balance in a potent lineup. Last season, LaRoche hit 33 home runs with a .271 batting average, .343 on-base percentage, .510 slugging percentage and 100 RBI. His slick fielding saved innumerable throws in the dirt. His bat and glove together earned a tie for sixth in the National League most valuable player voting.

“My respect for Adam LaRoche is second to none,” Rizzo said. “I wanted to do what’s right by him. He was the guy we really wanted on the ballclub.”

With LaRoche entrenched at first base, the Nationals will seemingly be forced to try to trade Morse, who no longer has a place in the starting lineup. Manager Davey Johnson admitted at the winter meetings he could not foresee both LaRoche and Morse returning with Bryce Harper, Denard Span and Jayson Werth taking up any potential outfield spot for Morse.

The Nationals would prefer to receive young starting pitching prospects or a major league reliever with a controllable contract in return. Morse has one year remaining on the two-year extension he signed last winter at $6.75 million.

Rizzo said he has been fielding calls about Morse for roughly the past month. Rizzo did not rule out keeping Morse, surely in part to avoid the impression that he would accept lesser value.

“There’s not going to be a time limit when we’re going to do it and if we’re going to do it,” Rizzo said. “If we can get the right deal for Mike, we’ll certainly think about trading him. We’re not going to make a bad deal just to move the player out of town. We don’t have to do it financially.”

The offense-poor Mariners and Orioles have shown interest in Morse. One major league executive speculated based on roster needs and makeup that the Yankees and Rays could make a play for him.