The U.S. Republican Party has formally opened its national convention to nominate presidential candidate Mitt Romney, but it postponed most of the first day's proceedings Monday as a tropical storm skirted the coastline of Florida, the southeastern state hosting the event.

Republican National Committee chairman Reince Priebus gaveled in the four-day convention in the city of Tampa, and immediately adjourned the session as party officials rescheduled speeches and other events for the remaining three days.

The delay was prompted by Tropical Storm Isaac, which forecasters said would pass more than 300 kilometers to the west of Tampa as it moves and strengthens across the Gulf of Mexico.

Romney aide Russ Schriefer told reporters in Tampa that the campaign is concerned about the people in the path of the storm and may revise the convention's schedule again.

Some Republicans expressed concern that Isaac could overshadow the event if it makes a destructive landfall on the U.S. Gulf Coast later this week. They said such a development may prompt the party to tone down the gathering's celebratory nature.

The Republican governor of the Gulf Coast state of Louisiana, Bobby Jindal, canceled his planned convention speech, saying he was staying home to deal with the prospect of Isaac hitting the state as a hurricane this week.

A Washington Post opinion poll published Monday shows President Barack Obama, the Democratic incumbent, and Mr. Romney in a tight race for the November presidential election. It says Mr. Romney has the support of 47 percent of likely voters compared to 46 percent for Mr. Obama — little changed from early July's figures.