The 32-year-old has already indicated he might rethink his retirement decision if England come calling, although that would be unlikely to happen ahead of this season's RBS 6 Nations Championship, which kicks off in February.
"I know Jason has expressed an interest in playing for England again," said England head coach Andy Robinson, following his elite squad's three-day training camp at Loughborough University.
"But the timing has got to be right for Jason. At the moment, he is not fully available to play international rugby."
World Cup-winner Robinson captained England in his final season of Test rugby, calling time after collecting 35 caps and scoring 22 tries during a four-and-a-half-year international career that also included two Lions tours.
The former rugby league star would relish working with England's new attack supremo Brian Ashton, who is part of a new-look coaching support staff alongside John Wells and Mike Ford.
Robinson featured as a full-back, wing and centre in England colours, and there can be little doubt he would make the World Cup squad, if available for selection.
Coaching chief Robinson declared himself satisfied with the Loughborough camp, although he has already ruled out five injured players from the Twickenham clash against World Cup favourites New Zealand on November 5.
Bath lock Steve Borthwick, Northampton hooker Steve Thompson, Gloucester wing James Simpson-Daniel and Newcastle star Jonny Wilkinson will not be considered to face the All Blacks, joining Bath prop Matt Stevens on the sidelines.
Robinson though, revealed he has a fairly good idea about the starting line-up to face New Zealand, and he is determined that injuries will not derail his plans.
"It was a really positive few days. There has been a positive approach, and the work we have been able to do has been of a fair quality," he said.
"There will always be injuries, but you have just got to get on with it.