Multiple media reports Sunday said the sides were close to an agreement on an eight-year contract extension worth $58 million. Letang has one year left on a contract that pays him $3.5 million annually.
"It's simpler enough to say we're just not done yet," Shero said Sunday at the NHL Draft in New Jersey, according to the team's website. "Still working on it with his agent. We haven't had time to get together today with the draft. I'll talk to him a little later [Monday] and try to work through a couple of things and get back at it."
Letang, who was the Penguins' third-round draft pick (No. 62) in 2006, had 38 points in 35 games in 2012-13 and was a Norris Trophy finalist. He has 209 points in 385 career regular-season games since making his NHL debut on Oct. 5, 2006. He was a member of the Penguins' Stanley Cup-winning team in 2009 and has 47 points in 80 Stanley Cup Playoff games.
"I had a meeting with [Letang's] agent [Saturday] afternoon and later that night when we chatted again it turned more positive," Shero said. "This morning we were trying to wrap a few things up, but we're still not there yet. We just took a little break. We'll get back at it and see if we can close the gaps here and there and see where we are.
"It usually comes down to the money and the term. There are things we still need to work on. We’ll see where it takes us."
The Penguins also are in discussions with forward Pascal Dupuis, who can become an unrestricted free agent July 5. Dupuis, who made $1.5 million in 2012-13, scored 20 goals in 48 games.
"He's an important piece of our team that I'd like to have back," Shero said of Dupuis. "The money and the term have to fit both parties. We're still not there yet. We'll continue to work on it. We'd like to have him back, if at all possible."