His twin brother, forward Joel Lundqvist, is Sweden's captain.
The Rangers were eliminated from the 2017 Stanley Cup Playoffs with a 4-2 loss to the Ottawa Senators in Game 6 of the Eastern Conference Second Round at Madison Square Garden on Tuesday.
"I haven't played with [Joel] in 12 years," Lundqvist said Thursday. "I see this as an opportunity to play for my country one more time and with my brother. So I'm going to go there and I'm going to try to finish really strong this season."
Lundqvist said he made the decision Wednesday to go to the World Championship. His first game is expected to be Sunday, when Sweden plays a Group A preliminary round game against Denmark.
This is the first time Lundqvist will play in the World Championship since 2008. He played for Sweden in the 2010 Vancouver Olympics, the 2014 Sochi Olympics and the World Cup of Hockey 2016.
"There's a lot of gas left in the tank here," Lundqvist said. "I was hoping to play [in the Stanley Cup Playoffs] for another month. That was our goal and my mindset. It was very disappointing obviously to end the season like we did, but you have to accept … it's over here. The last two days I've been just thinking about what I could have done differently, what I could have done better. I probably won't have all the answers until a few weeks. I'm going to continue to think about this. But right now, after spending so much time the last two days to think about it, I made the decision to go play for Team Sweden with my brother and analyze a little bit more after that."
Sweden, which played Latvia later Friday, has a regulation win against Germany, a shootout loss to Russia and a regulation loss to the United States.
