Jos Buttler's England have only a mathematical chance of making the semi-finals and a loss to their Ashes rivals will end their title defence.

Australia, meanwhile, sit third and are in ominous form after four consecutive wins.

Root said England, however, should be top of the table with the quality in their squad, and the players were "all very frustrated that wasn't the case."

"Man for man, I'd have this team every day over the Australians," Root told British media.

"We might not have played as well as we can do but we know when we play our best stuff, the best teams struggle to compete with us.

"We've just got to look at Saturday as our World Cup final and play in the manner that's expected of us and we expect of ourselves."

Australia captain Pat Cummins struggled to stifle laughter when asked about England's campaign following the champions' fourth defeat to Sri Lanka, saying it was "sad to see".

Root said England would probably be laughing, too, if positions were reversed.

"It hurts - it always hurts to be in this position to be sat at the bottom of the table. It's not what we expect of ourselves. If it motivates us a little bit more, then great."

Root's form has mirrored his team's fortunes, with scores of 0, 3, 2 and 11 in his last four innings.

He said he felt "really good in (his) game", while blaming a mix of poor luck and a tough lbw call for some of his dismissals.

"It's been really disappointing to not be more consistent. That's what I expect of myself," he added.

"Saturday is another opportunity to go and score runs, do what I expect of myself and what the team expects of me."