Both players are due to be free agents at the end of the season.
"We're talking to the representatives of both players. We'll be doing that over the next few weeks," Lawwell told Sky Sports News.
"It's the first meeting we'll have with Georgios' representatives. We've been talking regularly to Joe's and hopefully we'll get something tied up before the end of December."
Celtic continue the defence of their Scottish Premiership title on Saturday when they play host to Dundee United.