Chambers won silver at this month's World Indoor Championships

Cas have called a press conference for Monday morning, although Chambers' spokesman Damion Silk says he is yet to make a commitment to the club.

Chambers, 29, returned from a two-year drugs ban to win 60m silver at this month's World Indoor Championships.

He spent a brief spell playing American Football after his suspension ended.

UK Athletics made it clear they did not want Chambers representing Britain at the World Indoors in Valencia despite including him in the squad.

And, after he had finished second behind Nigeria's Olusoji Fasuba in the final, Chambers hinted at quitting athletics because of the opposition to his participation at top level meetings as well as at this summer's Beijing Olympics.

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BBC Sport's athletics correspondent Mike Costello told BBC Radio 5 Live: "If we think back to what Dwain was saying after the World Indoor Championships then perhaps it is not surprising he is leaving athletics - what is surprising is that he is going to rugby league.

"He was talking then of moving outside of athletics because he was being forced outside.

"He was told by all the promoters at the top meetings around Europe - where all the best athletes earn the most money - that he is not welcome at any of those meetings ever again."

Cas need a couple of tried and trusted rugby league players rather than a circus act rolling into town BBC Sport's Dave Woods

Chambers was thought to be considering an appeal against the lifetime Olympic ban the British Olympic Association imposed upon him after tested positive for the performance-enhancing drug THG in 2003.

But a move into rugby league would signal the end of his Olympic dream.

"At the moment this is a huge relief for UK Athletics and of course the BOA," Costello added. "He is 29 so Beijing was his last chance at top level for sure.

"But these are just talks and there is no guarantee he will go to Castleford and make a success of rugby league, so what happens then?"

Chambers joined the Hamburg Sea Devils at the start of 2007 after impressing at an NFL Europa training camp in November 2006.

But his debut season was ended by a fracture to his right foot and the competition has since folded.

"That crumbled and he came back to athletics," Costello added.

Castleford have won just one of their opening eight matches this season since their return to Super League and have the smallest squad in the top flight.

It is believed the Tigers have room under the salary cap to sign Chambers, who is not thought to have played rugby league before.

BBC Sport's Dave Woods added: "You would have thought that Cas need a couple of tried and trusted rugby league players rather than a circus act rolling into town."

Chambers would not be the first high-profile athlete to turn to the 13-man rugby code - British 100 yard record holder Berwyn Jones joined Wakefield Trinity in 1964.

Jones was included in Great Britain's squad for their 1966 tour of Australia and played the sport for five years.