Martin O'Neill will not discuss deals with his out-of-contract players until Sunderland's Premier League fate this season is decided.
Defenders Titus Bramble and Matt Kilgallon are in the final months of their current agreements, and Bramble has consistently said he would like to stay.
The centre-half is back in favour and has started 10 games in succession, but with Sunderland in a fight for Premier League survival his future will remain unclear until the summer.
O'Neill told the Sunderland Echo: "Now, at this minute, the most important issue is trying to get points on the board.
"I know it's a cliche, but those things can wait."
Sunderland have taken just two points from a possible 18 and go into this weekend's game against Norwich just six points above the bottom three.
O'Neill's side face a daunting run of fixtures after Norwich as they take on Manchester United, Chelsea and Everton either side of a derby at Newcastle.
The match is being organised in conjunction with the club's proposed new owners the Pompey Supporters' Trust, with all proceeds going towards their community stake in Portsmouth, and will take place at Fratton Park on Tuesday, April 16.
Defender Hreidarsson, 38, who made 123 appearances for Pompey, is paying the expenses to bring his side to the south coast as part of an eight-day tour of England ahead of the new Icelandic Premier League season.
PST chairman Ashley Brown said: "We were delighted when Hermann approached us with this idea. This is a fantastic opportunity for fans to come and say farewell to a terrific club servant, but more importantly contribute to the biggest community share yet.
"Every penny will be reinvested in the club as part of the PST's shareholding, so this means any fan can have their stake in Pompey simply by buying a ticket for the match.
"More details of prices will be announced soon, but no standard ticket will cost more than ?10, so we feel this is a great way to make community ownership accessible to all."
Hreidarsson, who has recently been in England to complete a coaching course, added: "It is a great opportunity for my players to play at a legendary ground and all the money will be going to a great cause.
"My time at Pompey was a rollercoaster ride, with some terrific highs like winning the FA Cup in my first season and also some difficult times, which saw some good people lose their jobs.
"All the time, though, the Pompey fans were different class and I didn't feel I got the chance to say goodbye to them properly after I was left for Coventry in 2012."
The 24-year-old South Africa international is hoping to be included in Doncaster's squad for Saturday's home game with Portsmouth.
Furman is currently in his fourth season at Boundary Park after signing from Rangers in 2009 and has made over 120 appearances for the club.
He began his career at Chelsea under Jose Mourinho then moved to Ibrox in 2008 and had a loan spell at Bradford before signing a three-year deal with the Latics in the summer of 2009.
Furman made his debut for his country in a friendly against Brazil in September 2012 and earned the man-of-the-match award in South Africa's 2-0 win over Mozambique later the same year.
