(AP) - Republican officials abruptly announced plans Saturday evening to scrap the first day of their national convention, bowing to a threat posed by Tropical Storm Isaac, churning toward Florida.

"Our first priority is ensuring the safety of delegates, alternates, guests, members of the media attending the Republican National Convention, and citizens of the Tampa Bay area," party chairman Reince Priebus said in an emailed announcement that followed private conversations involving presidential candidate Mitt Romney's campaign, security officials and others.

Priebus added that forecasters have predicted that convention-goers "may encounter severe transportation difficulties due to sustained wind and rain" on Monday, the day the convention had been scheduled to open.

The announcement said that while the convention would officially be gaveled into session on Monday as scheduled, the day's events would be cancelled until Tuesday.

That meant Romney's formal nomination would be postponed by a day, from Monday to Tuesday, but the balance of the four days of political pageantry and speechmaking would go on as scheduled.

The former Massachusetts governor campaigned in battleground Ohio during the day, pledging to help women entrepreneurs and innovators who are eager to create small businesses and the jobs that go with them. It was an economy-themed countdown to the Republican National Convention taking shape in a city already bristling with security - and bracing for a possible hurricane.

"Women in this country are more likely to start businesses than men. Women need our help," said the Republican presidential challenger, eager to relegate recent controversy over abortion to the sidelines and make the nation's slow economic recovery the dominant issue of his convention week.

The former Massachusetts governor campaigned with running mate Paul Ryan in battleground Ohio as delegates arrived in Florida by the planeload. Across town, technicians completed the conversion of a hockey arena along Tampa Bay into a red, white and blue-themed convention hall.

The announcement made the GOP convention the party's second in a row to be disrupted by weather. Four years ago, the delegates gathered in St. Paul, Minn., but Hurricane Gustav, slamming the Gulf Coast, led to a one-day postponement.

In that case, party officials rewrote their script to make President George W. Bush's speech into a video appearance, and to cancel plans for Vice President Dick Cheney to appear before the delegates. Both men were unpopular at the time.

Four years later, there was no immediate sign that Romney's forces would do anything other than squeeze two nights' of platform programming into one. Nor did it appear the postponement would cost them much, since the television networks had already announced they would not be carrying any of Monday's events live.

There was no hint in the announcement of a postponement of plans to evacuate the roughly 2,000 delegates eager to nominate Romney and Ryan as their ticket for the fall campaign.

"Federal, state and local officials assure us that they are prepared to respond, if needed, and the scheduling changes we are announcing today will help ensure the continued safety of all participants - our foremost concern," the announcement said.

"We are also committed to keeping the delegates and guests of the convention well informed about the situation, and we will continue providing updates in the hours and days ahead."

Despite the disruption, Priebus said, "we are optimistic that we will begin an exciting, robust convention that will nominate the Romney-Ryan ticket."