Jackson said that, despite being the favourite, victory was not a foregone conclusion.
"You can never be too confident," he said. "There are 10 hurdles and it only takes one mistake to blow it."
And Jarrett, the man who finally grabbed gold when his career-long nemesis skipped the Games in Kuala Lumpur four years ago, insists he will not give up the title without a fight.
"I hope to retain my title and I wouldn't be here if I didn't think I could," said Jarrett.
"I am going in the right direction and it is so far, so good.
"The crowd are just beautiful and I would feel very proud to successfully defend my title in Manchester."
Scotland's Chris Baillie is also in the final having qualified as a fastest loser.