The final piece of Alex Smith's move to the Washington Redskins is now officially in place.

Smith, who was traded to the Redskins by the Kansas City Chiefs in January in a move that became official on Wednesday, signed an extension with Washington on Thursday.

Terms of the deal were not disclosed but reports at the time of the initial trade agreement indicated it is a four-year contract that could be worth $94 million, with $71m guaranteed.

Smith was dealt to the Redskins in exchange for a third-round pick and cornerback Kendall Fuller. As a result of Smith's arrival, Washington allowed quarterback Kirk Cousins, who is expected to sign the richest contract in NFL history with the Minnesota Vikings, to hit free agency.

"I feel like I've been waiting for this for a long time. For it to finally be official, it's like get in the building and be here and kind of start the process," Smith told the Redskins official website. 

"So I'm excited for it. I’m excited that we're here now and get the ball rolling.

"There's so many different things that go into winning football games and striving to win a championship, there's so many different inputs and I think it's finding a way to take those all together and we all have a hand in it, we all have a part in it.

"And how can we figure out to go out there and win ballgames. And win the division, get into the playoffs and win a championship. That's what everybody's striving to do... We've got to figure out how this team is going to do that."

The former San Francisco 49ers signal-caller led the Chiefs to four playoff appearances in the past five years and threw for 102 touchdowns and 33 interceptions in that span. Last year alone he threw for 4,042 yards and 26 touchdowns. 

The start of the 2018 season will be 33-year-old Smith's 14th year in the league.