Dinesh Chandimal has scored an unbeaten 63 as Sri Lanka struggled to 136-5 at lunch on Day 3 in reply to Australia's imposing first innings of 654 in the first cricket test.

Australia's Usman Khawaja struck a maiden double hundred and Josh Inglis got a century on his test debut against Sri Lanka to power the tourists to a mammoth 654 for six before they declared their first innings on day two of the opening test on Thursday.

Australia may be about to enter a new era of overseas Test cricket on free-to-air television as Seven prepares to broadcast the Sri Lanka series starting this week, a harbinger of future bidding for matches in India and elsewhere.

Australia had Sri Lanka three down after opener Usman Khawaja’s first double century and a ton on debut by Josh Inglis helped the tourists to 654-6 declared in the first match on Thursday. Sri Lanka were 44-3 by stumps on day two at Galle with senior batsmen Dinesh Chandimal,

Travis Head will replace Sam Konstas as Usman Khawaja's opening partner in the first test against Sri Lanka at Galle on Wednesday, Australia's stand-in captain Steve Smith said on the eve of the match.

With Australia in a commanding position during their opening innings against Sri Lanka, Inglis arrived at the crease with no intention of taking things slowly.