Former Sunderland defender Stanislav Varga will sign for Celtic providing he completes a successful medical on Monday and the Parkhead club secure a work permit.

He will join the Scottish champions until the end of the season with an option for another year after signing a pre-contract agreement with the Scottish champions.

But Croatian international Milan Rapaic failed to prove his fitness to Celtic boss Martin O'Neill after joining Varga in Glasgow on trial.

Varga, a Slovakian international, was released by Sunderland and is keen to follow in the footsteps of his countryman Lubomir Moravcik - a Celtic hero.

Moravcik enjoyed four happy years at Parkhead, during which time he earned cult status at the club.

Varga is currently unemployed and will be able to sign for the Glasgow club despite the closure of the transfer window.

But the Slovak will not be eligible to play in Celtic's Uefa Cup matches against Stuttgart.

We're certainly taking him on until the end of this season and, beyond that, we'll just have to wait and see Celtic boss Martin O'Neill

Manager O'Neill is seeking depth as his side are still chasing three other titles and Varga might be useful cover for injured Swedish central defender Johan Mjallby.

O'Neill has thrown down the gauntlet to the player, challenging him to earn a longer-term deal.

The Irishman told the club's official website: "The situation is that, subject to everything being right, we hope to take Stan on until the end of the season.

"Obviously we're concerned about injuries, and Varga is an experienced international player who's played at the top level in the Premiership.

"The rest is up to him. He knows what he has to do, and also the calibre of player he's competing against.

"But he's hopeful of making an impact. We're certainly taking him on until the end of this season and, beyond that, we'll just have to wait and see."

His (Rapaic's) situation is one we'll be looking at over the next day or so Milan Rapaic

Varga, capped six times for his country, only made 28 starts in his three seasons with Sunderland after his �875,000 move from Slovan Bratislava.

Celtic have also been linked with Croatian international Rapaic, who joined Varga at Celtic training last week.

O'Neill revealed that a final decision has still to be made on the former Fenerbache striker.

O'Neill said: "There's no questioning that he has a very good pedigree, but his fitness is something we'll need to consider.

"It's some way off what we would like it to be, although that's understandable given that he's played very little football with Fenerbache over the last couple of months.

"His situation is one we'll be looking at over the next day or so."

O'Neill may be forced to bring Rapaic to Parkhead on a short-term basis with his star striker Henrik Larsson ruled out for six weeks after breaking his jaw against Livingston.