The NRL has told the PNG Chiefs that any contract for Hudson Young must be registered at his $1.1 million market value, matching Canberra's annual offer.
The Raiders have now increased their bid to retain the back-rower, adding a year to their initial lucrative proposal.
If Young accepts, he will remain in the nation's capital until the end of 2031.
Young is on holiday and is due to meet Canberra officials next week to discuss the improved offer.
The Raiders hope the deal will keep the Chiefs from signing him after the PNG club had been considered the favourite.
The Chiefs were understood to be prepared to offer $900,000, but that figure is below the amount the NRL says must be used for registration.
Despite the lower salary, tax breaks available on Chiefs contracts would leave Young with greater take-home pay than Canberra's offer.