The Centenary rugby league Test and next week's NSW City-Country Origin clash will both be played under international rules, with 12 interchanges per team.

The Australian Rugby League on Thursday announced both matches will feature the 12 interchanges from four replacements format rather than the current NRL system of 10-4.

Test matches are required to be played under international rules unless the two participating countries agree otherwise.

ARL chief executive Geoff Carr said player welfare played a major part in the ARL and New Zealand Rugby League's decision.

"We were mindful of the fact many players selected for this match will be backing up to play the next day," Carr said of the May 9 showpiece at the SCG.

"Likewise the NSW Rugby League and Country Rugby League wanted to ensure the City-Country Origin players were not overworked during this period.

"The international rules allow for two extra interchanges per match compared to the NRL system and this will benefit those players.

"In the case of the Centenary Test, it is in the interest of both teams to play under international rules as the upcoming World Cup will be in that format."

The ARL is yet to decide what rules to apply to the State of Origin series.

Origin is typically played under NRL guidelines and, given the games are played on Wednesdays, it could be possible to stick to a 10-man interchange because of the longer recovery for players until their weekend NRL games.

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