The New Zealand-born number eight has been sidelined since suffering a serious knee injury six months ago.
He could not play a full part during England's World Cup training camp in Portugal earlier this month, but his recovery process has now hit the accelerator.
And Ashton also believes the time Ward-Smith spent working with renowned knee injuries expert Bill Knowles in America is a significant contributory factor.
Ashton said: "I am delighted with Dan. Not that long ago it looked less than 50-50 for him, but he is back in and doing full training with full contact.
"The work he did in the USA has pushed him along really, really well.
"Dan is a determined character, and once he saw a tiny little bit of light at the end of the tunnel then he has really gone for it.
"Going across to America and having specialist one-on-one attention - added to his determination - has accelerated his progress quite dramatically. He is an incredibly fit athlete."
But while Ward-Smith's World Cup prospects have brightened considerably, Gloucester centre Mike Tindall continues on the long road back to full fitness.
Ashton believes it is "highly unlikely" 2003 World Cup-winner Tindall will be in contention for England's warm-up clash with Wales at Twickenham on August 4.
That would then leave the Gloucester centre with just one more game - against France at the same venue seven days later - before Ashton announces his 30-man World Cup squad on August 14.
Tindall, who has won more than 50 caps, is recovering from a broken leg suffered during Gloucester's Guinness Premiership clash against Newcastle in April when he collided with England colleague Toby Flood.
Ashton added: "We probably need to make some sort of call over the next couple of weeks.
"It is ongoing rehab with Mike, but of all the players who are currently rehabbing he is well behind the others.
"It is highly unlikely the way things are at the moment that he will be fit for the Wales game."