A source told ESPN.com's Pierre LeBrun that the deal is worth $3 million -- $1.5 million for each season.
Erskine is in his fifth season with the Capitals and ninth in the NHL. He has three goals -- a career high -- and four assists this season.
Erskine finished last season with a career-best plus-16 rating, his third straight season with a plus rating. He is plus-3 this season.
In his career, Erskine has appeared in 354 career NHL games with Dallas, the New York Islanders and Washington, recording 10 goals, 28 assists and 673 penalty minutes.
Information from ESPN.com's Pierre LeBrun and The Associated Press is included in this report.