Canberra withdrew Hudson Young's extension offer last week.
"The offer that was made was the largest in club history. As a club, we believe we have done all we can to keep Hudson in Canberra," a Raiders statement read.
The club said negotiations had run since June and it needed an answer by October's end to plan ahead.
The statement added: "Hudson remains contracted to the Raiders for the 2027 season, and we look forward to seeing him return for pre-season training."
Young and PNG Chiefs football head Michael Chammas will visit Port Moresby on Wednesday morning to consider a possible 2028 move.
The Courier Mail reports the NRL rejected an initial offer as below market value, but a reported $3.6 million deal may now be approved.
The Chiefs need forwards, with Matty Lees their only registered middle; Young has played 155 NRL games, six Tests for Australia and nine for NSW.
Jarome Luai, Brian To'o, Zac Lomax and Joey Manu have committed for 2028 after visiting Port Moresby.