It is a great achievement for two master batsmen but given their competitive nature, only a win at the WACA will allow either to really enjoy passing what was once the rarest of milestones.
For Clarke, victory would secure a 3-0 series triumph and the return of the coveted urn after three consecutive Ashes defeats at the hands of his country's greatest sporting rival.
"I think that's why it's most special for me, that we have the chance to win the Ashes," Clarke told reporters at the WACA on Thursday.
"It's obviously fantastic that I've been able to play 99 tests for my country, something I'm certainly proud of, but in regards to it being my 100th test match, it's not my focus, there's enough other reasons why this match is special to me and this team."
For Cook, a first win for the tourists in Perth since 1978 would arrest an alarming decline in the fortunes of the England team since they arrived in Australia charged with confidence after a dominant 3-0 win back home earlier this year.
"It's a huge honour to join the hundred club and one I thought I'd never get to," the 28-year-old told reporters.
"It is a special day and it will make it an even more special week if we can produce the sort of performance we know we're capable of."
That they both reach the milestone in what could be the decisive moment of an Ashes series should not detract from the achievement of two players who will one day go down in the record books as the best their countries have produced.
Clarke is four years the senior and has just edged ahead in the statistics during this series with 26 test centuries to Cook's 25 and 7,940 runs to the Englishman's 7,883.
"I think he deserves a lot of credit for the success he's had over a long period of time and his record is something he should be really proud of," Clarke said.
"He's a wonderful guy, I really enjoy playing against him. He's a very good captain. He's always been a prize wicket for the Australian team and this test match is no different."
Cook repaid the compliments in kind.
"It's strange isn't it How it's both captains in the same game," said Cook.
"He's obviously had an incredible career and he's been the leading batsman (in the world) for the last couple of years.
"We've had a fair few battles along the way, both of us, and he's one of these guys when you stop playing cricket you'll remember playing against him.
"It's great sharing it with him."
Where the pair would have differed before this series was in their relative success as captain, with Cook well ahead of his Australian rival.
That is not the only thing that has been turned around over the two tests in Brisbane and Adelaide and Cook admitted that his 100th test was probably the biggest challenge he has faced since becoming skipper.
Cook is the youngest player to reach a century of tests, having achieved the feat in just under eight years since his debut in early 2006.
He was not about to be drawn on whether he might one day match Sachin Tendulkar's record of 200 tests, which the Indian great recently sealed in his final match before retirement.
"Who knows I've just got to cherish every one I play, I'm privileged to play a hundred and I hope to play a fair few more," Cook said.
"It would be wrong to presume anything but if people want me to play, I'll go on for as long as I can.
"(200 tests) is a long way away."