Eddie Jones is hoping George Ford does not rule himself out of international contention by moving to the Top 14, having reiterated he will continue to ignore any player that leaves England's Premiership for France.
Bath fly-half Ford has been linked with a switch to Toulon, who are now coached by his father, Mike.
Yet the Rugby Football Union (RFU) has a policy of overlooking players who ply their trade outside of England, meaning the likes of Steffon Armitage and Nick Abendanon - the European players of the year in 2014 and 2015 respectively - have missed out on selection.
"We don't want to lose George, but ultimately he's got to make a decision," Jones told reporters in Portugal, where England are holding a training camp ahead of upcoming Tests against South Africa, Fiji, Argentina and Australia.
"It's an easy choice: you either sign for an English club or a French club. If you sign for a French club, you don't play for England.
"I want players who want to play for England. If he doesn't want to play for England, so be it."
Jones is fully supportive of the RFU's stance regarding players who move overseas.
"You've only got to look at what's happened in France, where foreign players have been allowed to escalate to over 50-60 per cent and you have massive problems for the national game," added the Australian.
"You take some short-term pain for the long-term gain. This is not an Englishman talking. For the long-term future of the game we need to look after the Premiership.
"To be the number-one team in the world we need players with the absolute desire to play for England. So there's no choice here. If you want to play for England, you play for an English club. There's no more discussion."
Jones also revealed that a desire to produce "brutal" defence prompted the decision to recruit Melbourne Storm assistant coach Jason Ryles on a short-term basis.
Explaining the decision to bring in a coach from rugby league, Jones said: "We want to bring that harder edge towards our defence so Jason's in for a couple of weeks to assist [defensive coach] Paul Gustard. I think he'll make a hell of a difference.
"There are certain technical things we can learn from rugby league and Jason brings them to the party. To beat the Springboks we need our defence to be absolutely brutal and that's something we'll be practising this week."