"I have something very, very big concerning the president of the United States," said Trump on "Fox and Friends."
Trump, who said the surprise announcement will most likely be revealed on Wednesday, declined to give any specifics on the information he plans to share.
When pressed on whether his information would change the outcome of the election, Trump said, "Possibly.
"It's very big, bigger than anyone would know," he added.
The reality television host was a prominent figure during the Republican primary race, seeking to influence the outcome and holding meetings with most of the GOP presidential hopefuls. Now a surrogate for Republican presidential nominee Mitt Romney, Trump has been an outspoken critic of Obama's foreign and economic policies.
He recommended that the GOP contender take an "aggressive" approach during Monday night's third and final presidential debate, which will be focused on foreign policy.
"I think Romney should be very, very aggressive, because the target is so easy. This is the worst foreign policy in history. You look at his Middle East. I mean, I got a kick before when they were saying he's the more experienced person, meaning Obama. It's the worst foreign policy in history. The Middle East is crumbling down and they hate us," Trump said.
Back in August, Trump promised a "big surprise" ahead of the Republican National Convention, but remained similarly coy in the lead-up to the announcement.
His "surprise" event was canceled due to the threat from Hurricane Isaac, but was later unveiled on NBC's "Today" show. An "Apprentice"-style video, featuring Trump delivering a mock performance review to the president, was set to air during the Tampa convention, reported NBC.