Australia would appear to be underdogs heading into the final day of their first Test with Sri Lanka in Pallekele, but batting coach Stuart Law insists the tourists remain confident of securing victory.

Steve Smith's side require a further 185 to win, with seven second-innings wickets intact, after ending day four on 83-3.

Kusal Mendis, whose brilliant 176 turned the match on its head, is the only player to have passed 50 on a pitch offering increasing turn.

Yet Law believes the time lost in the match to rain and bad light means Australia will not be facing a typical fifth-day wicket when they aim to complete a daunting chase.

"It's not going to be a day-five pitch," said Law. "We have played like three days. History says that teams have chased down big totals in the last innings [here].

"This [pitch] doesn't look like it's deteriorating a great deal. There's not many marks on it. You walk out there and big Mitch Starc has been bowling left-arm over for a few overs and he's hardly broken the surface. It's as hard as concrete and it's very dry.

"Overnight these conditions do tend to get the moisture back up into the surface, so the first half-hour to an hour can be tricky. But the wicket's dry enough now. I don't think that will be an issue.

"If we get a full 90 overs in a day's play, it should be a very interesting finish to the game.

"We're still very confident. We want to play to win games of cricket, we don't play to draw, so we're just waiting to see what tomorrow brings weather-wise and then we can really have a crack at it."

Sri Lanka coach Graham Ford was also optimistic as he looked ahead to the final day.

"I think we've fought really hard to get ourselves into a situation where we can still win this Test match," said Ford.

"Pleasingly, a few balls started to turn quite sharply just before the players came off for bad light. I'm hoping tomorrow [Saturday] a few things will go our way and we'll be able to press home and finish off with a good victory."

Ford hailed Mendis' epic knock as "one of the best innings I've ever seen", adding: "He is an amazing talent, works really hard and really loves the game so it's very exciting for Sri Lankan cricket. Nothing really fazes him."