Damon Winter/The New York Times

TAMPA, Fla. — Republicans on Saturday canceled the opening day of their national convention, saying their first concern was for the safety of delegates and guests in the face of Tropical Storm Isaac, which is strengthening and is headed toward Florida’s West Coast.

“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,” Reince Priebus, the chairman of the Republican National Committee, said in a statement.

“R.N.C. convention officials and the Romney campaign are working closely with state, local and federal officials, as well as the Secret Service, to monitor Tropical Storm Isaac and preserve Florida’s emergency management resources,” he said. “Officials have predicted participants may encounter severe transportation difficulties due to sustained wind and rain.”

The convention will officially open on Monday but will immediately recess until Tuesday afternoon at a time to be determined later, Mr. Priebus said.

Planners stressed that the official business of the convention will go on as planned later in the week.

“The Republican National Convention will take place and officially nominate Mitt Romney and Paul Ryan, and the party has other necessary business it must address,” Mr. Priebus said in the statement. “We also are remaining in constant contact with state and federal officials and may make additional schedule alterations as needed.”

Canceling the first day disrupts a carefully planned schedule that had been intended to highlight Mr. Romney’s qualifications and offer a critique of President Obama.

The opening day was to have been called “We Can Do Better,” featuring speakers who would address what they considered to be the failures of Mr. Obama’s administration. Planners had said “real people who have been affected by the Obama economy” were scheduled to speak.

Officials said the roll call vote of the states nominating Mr. Romney would take place on Tuesday. And they expressed confidence that the message of the convention would be effectively made in three days.

“We will absolutely be able to get our message out,” said Russ Schreifer, a top aide to Mr. Romney. “We still have an opportunity to tell the story of the last four years of how President Obama has failed the country.”

He added, “We think we can absolutely do it in three and we look forward to telling that story.”

Among the speakers scheduled to address the delegates on Monday were Jeb Bush, the former governor of Florida, and Nikki R. Haley, the governor of South Carolina. Mike Huckabee, the former governor of Arkansas, and Florida’s current governor, Rick Scott, were also supposed to speak on Monday.

They and the other speakers may be rescheduled and fit into the other three days. Republican officials said they would make announcements about a new plan as soon as Sunday morning.

“We have been working closely with the campaign, the party and state and local officials for months to ensure a successful, enjoyable convention,” Bill Harris, the chief executive officer of the convention, said in a statement. “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.”

The main three broadcast networks had already deemed the first day to be less interesting than the rest of the convention and decided not to carry any of the prime time speeches live. In response, convention planners had moved Ann Romney’s speech from Monday to Tuesday.

The weather situation was eerily reminiscent of four years ago, when a hurricane in the Gulf of Mexico also forced the cancellation of the first day of the Republican convention.

But in 2008, Republicans were meeting in Minnesota. Because the hurricane had the potential to hit New Orleans, convention planners decided they did not want to risk a poor reaction from voters watching partisan speeches as people suffered along the Gulf Coast.

As of Saturday evening, Tropical Storm Isaac was headed into the Gulf after battering Haiti. The track of the storm suggested that it could bring heavy rains and winds to South Florida and perhaps to Tampa.