Cameron White (43 off 31 balls) and Michael Hussey (60 off 24) took Australia past Pakistan's score of 191 for six, which had been the joint second highest total of the tournament.
"Hussey and White had an amazing day. I honestly felt Pakistan scored 15 runs too many for us but you just can't write us off, with the class and experience we have in this team," Clarke told reporters.
Australia will face England in Sunday's final at the Kensington Oval in Bridgetown after Clarke's men completed the highest successful run-chase of this competition.
"We will take a lot of confidence going into Barbados, our mindset, exactly what 'Huss' showed today is we are never beaten until the game is over," said the captain.
Hussey won the game by hitting three sixes and a four in successive balls in the final over.
FREAKISH PERFORMANCE
"Huss's was a freakish performance from an unbelievable cricketer. When we lost a few wickets it was always going to be hard to chase that total," said Clarke who was too tense to watch the finale.
For Hussey it was an innings he will never forget.
"I think that's probably the best feeling I have ever had on a cricket field. It is particularly good to score the winning runs in such a big game when I was having so many doubts," said the left-hander.
"I had a feeling it wasn't going to be our day when balls were lobbing over us in the field.
"At the end I was just trying to slog every ball for six, I knew he (spinner Saeed Ajmal) would try to spear a few fast yorkers in and if he'd done that I'd have been in trouble but he just missed his length," said Hussey.
Asked what he was thinking before the penultimate ball with just a single needed for victory, he said he was still stunned by his match-winning six.
"It is all a bit of a blur. To be honest on the last ball I just wanted to hit it off the middle of the bat. I'm so happy, it was so great to see elation on the boys's faces," said Hussey.
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