Joe Thornton scored 20 goals and posted 69 assists for the Sharks last season. ((Harry How/Getty Images))

The San Jose Sharks announed Saturday they have signed veteran forward Joe Thornton to a three-year contract extension worth $21 million US.

The new deal ties Thornton to the Sharks until the end of the 2013-14 NHL season.

"Joe stepped up and made a tremendous commitment to this franchise, his teammates and the fans in San Jose," Sharks GM Doug Wilson said in a statement. "We are very pleased that we now have another key piece of this team's core under contract for the next four seasons."

Thornton, 31, is earning $7.2 million this season, and was scheduled to become an unrestricted free agent on July 1, 2011.

Had he chosen to test the free agency waters, he would likely have been the biggest marquee name on the market. Instead, he decided to take a pay cut and re-sign with the Sharks.

Earlier this month, the Sharks named Thornton as their new captain, the eighth in the team's 19-year history. Thornton, a London, Ont., native, succeeded Rob Blake, who retired at the end of last season after a 20-year career.

"He has always been a team-first player and he has embraced the role of being the captain and leader of this team," Wilson said.

Thornton also captained the Boston Bruins, who drafted him first overall in the 1997 NHL draft.

San Jose acquired Thornton in 2005, and he has since put his stamp on the organization, scoring 20 goals and posting 69 assists last season. In 13 seasons, Thornton scored 287 goals and tallied 933 points with the Bruins and Sharks.

He won the Hart Trophy as the NHL's MVP in 2005-06 and helped Team Canada win Olympic gold at the 2010 Vancouver Games.