The 23-year-old Kruger is a restricted free agent and was tendered a qualifying offer by the Blackhawks.
“We are still working on this one," Kruger's agent J.P. Barry wrote in an email on Wednesday. “Marcus does not have salary arbitration rights so we have more time to continue to work on seeing if we can agree on something."
Kruger, who was drafted by the Blackhawks in the fifth round in 2009, has appeared in 125 regular-season games for the Blackhawks in the past three seasons. He had four goals, nine assists and a plus-3 rating in 47 regular-season games last season and had three goals, two assists and a minus-2 rating in 23 playoff games.
Kruger played mostly at center on the fourth line and was a key member of the penalty-killing unit last season. The Blackhawks ranked third in the league with an 87.2 penalty-killing percentage (18 goals in 141 chances) in the regular season and had a 90.8 percentage (seven goals in 67 chances) in the playoffs.
Blackhawks general manager Stan Bowman said after the season one of his offseason goals was to re-sign Kruger. Bowman said last week he hoped they could reach a deal in the near future.
The Blackhawks' offseason has included re-signing forwards Bryan Bickell and Michal Handzus and defensemen Michal Rozsival and Nicky Leddy, signing goaltender Nikolai Khabibulin and trading away forwards Dave Bolland and Michael Frolik for draft picks.