A bomb threat disrupted Rudy Giuliani's plan to unveil a huge tax cut in Melbourne, Fla., forcing the Republican presidential candidate to move across the street and make the announcement an hour late.

Giuliani was supposed to roll out what his campaign was billing as the "largest tax cut in the history of America" and the most aggressive plan of any presidential candidate. But the campaign said a "security issue" led them to move from the Harris Corporation headquarters to an airport hangar.

Law enforcement authorities later said that "issue" was a bomb threat that came in at about 1:30 p.m. ET. Authorities said the threat was not specific to Giuliani's visit -- but it was the first such threat the company has had in five years. The FBI is investigating the incident, and no device was found.

Meanwhile, Giuliani -- off to a late start -- assuaged any worries of those in the hangar to the threat.

"There's nothing to be concerned about," he said at the top of the speech, and then got into his plan.

Giuliani's campaign claims the tax plan would simplify the tax code by introducing the Fair and Simple Tax (FAST) form. The express form would give taxpayers the choice of doing their taxes on a single page. A 10 percent tax would be assessed on the first $40,000 earned, 15 percent on $40,000 to $150,000 earned and 30 percent on $150,000 earned and above.

The plan would also cut corporate tax rates from 35 to 25 percent, eliminate the estate tax and cut capital gains taxes from 15 to 10 percent. It proposes keeping the Bush tax cuts permanent.

The Republican presidential candidate is trying to raise his profile after placing fourth in the New Hampshire primary Tuesday and nearly finishing last in the Iowa caucuses last week.

The former New York City mayor, who has staked his presidential bid on his performance in the Jan. 29 Florida primary and on "Super Tuesday" on Feb. 5, has lost his lead in recent national polls as attention has focused on other Republican candidates.

FOX News' Mosheh Oinounou contributed to this report.