England captain Sean O'Loughlin has joined the debate over the Test against the Kiwis in Denver, arguing that the NRL has a duty to promote the international game.

The contentious match on June 23 has been sanctioned by the Rugby League International Federation, having been scheduled for the NRL's mid-season break.

However, some NRL clubs who are threatening to not release players, who they say will find the travel and altitude of the venue too physically demanding.

England coach Wayne Bennett and his eight NRL-based players have issued a statement confirming their support for the fixture at Denver's Mile High Stadium.

"I hope all the NRL boys get the nod," O'Loughlin said.

"I know the NRL are dragging their feet a bit.

"I'm not up to speed with all that's happening behind the scenes but I'm just hoping Wayne has the pick of everyone and it can be our strongest side that goes out there."

O'Loughlin says the international game needs to keep a strong foothold, while acknowledging the importance of the NRL club competition.

"The NRL are the biggest generators of income - they're a lot more successful money-wise than Super League and probably the international game - so they're holding the cards a little bit at the minute.

"But I still think they have a certain responsibility to promote the international game. We in Super League always want that to happen."

O'Loughlin welcomed the statement from his Australia-based teammates, arguing the importance of the mid-season fixture in the wake of England's World Cup campaign, in which they lost a tense final to Australia.

"It's big for the national side from our perspective that we back the World Cup up and get a win," said the Wigan back-rower.

"The atmosphere created during the camp was one of the best I've been involved in so I've no doubt all those players want to be part of it but it's probably down to the clubs and the NRL now."