Kearney suffered a calf injury on Monday while Earls has been struggling with a knee issue.

Andrew Conway and Jordan Larmour are likely to deputise if Kearney or Earls fail to prove their fitness in time.

Robbie Henshaw will definitely miss Sunday's game after injuring his hamstring in training on Saturday.

It is hoped that the Leinster centre will be fit for for Ireland's second Pool A game against hosts Japan on 28 September.

Joey Carbery and Earls have both trained this week after sustaining injuries in warm-up fixtures.

"Robbie won't make this weekend," said defence coach Andy Farrell. "We are very happy with his progress but he will sit out this weekend and hopefully he will be available for next week.

"We're pleased with how things have gone today. Rob and Keith ran well, and trained well.

"There's a few protocols that they need to go to, so that's what we need to adhere to with the medical staff. But they are very happy."

Munster winger Earls was injured in Ireland's final World Cup warm-up fixture against Wales

Kearney pulled up in training on Monday, which put "significant doubt" over his selection for the fixture.

Carbery was forced off against Italy in the opening warm-up game but has recovered from an ankle injury and is expected to take a place on the bench.

Ulster's Will Addison remains on standby after the injuries to head coach Joe Schmidt's backline, with Ireland management requesting that the full-back was rested from Saturday's pre-season friendly against Glasgow.

Kearney impressed in Ireland's 19-10 victory over Wales that closed their World Cup warm-up fixtures in Dublin on 7 September.

The 92-cap full-back ties Ireland's backline together and Schmidt will be keen to have his calming presence in the key pool match.