TAMPA,?US - US Republicans will delay the start of business at their national convention in Tampa, Florida by one day due to Tropical Storm Isaac, the Republican National Committee chairman said on Saturday.

Chairman Reince Priebus said the convention - originally scheduled to be a four-day extravaganza of pomp and party celebration - would convene on Monday as scheduled but then immediately recess until Tuesday afternoon.

The convention is due to formally nominate Mitt Romney and Paul Ryan as presidential and vice presidential candidates to challenge Democratic President Barack Obama and Vice President Joe Biden in the November 6 election.

"Due to the severe weather reports for the Tampa Bay area, the Republican National Convention is going to convene on Monday August 27th and then immediately recess until Tuesday afternoon, August 28th," Priebus told reporters in a telephone briefing.

He said members of the RNC, the Romney staff and officials who are running the convention made the decision unanimously in light of the weather situation.

Tropical Storm Isaac storm has pummeled Haiti, killing at least four people and has now moved on to Cuba.

Fueled by warm Gulf waters, Isaac was forecast to strengthen into a Category 2 hurricane with 100-mph (160-kph) winds and hit the US coast somewhere between the Florida Panhandle and New Orleans around midweek.

Officials expect to have a better idea of how badly the storm will impact the Tampa area by Sunday.

"The Republican convention is going to take place. We know that we will officially nominate Mitt Romney and Paul Ryan," said Priebus. He added that party officials were working with Florida state officials and emergency management to ensure the safety of everyone attending the convention.

Russ Schriefer, a representative from the Romney campaign, said they would adjust times and try to fit in as many speakers as possible in three days instead of the planned four-day event.

"I think the important thing is that, even as .. the days will be abbreviated, ... we'll absolutely be able to get our message out," Schriefer said.

"We have the opportunity to tell the American people the story of the last four years, how President Obama's failed leadership has failed this country and how Mitt Romney ... can provide a better future for Americans."

The Republican convention will bring 50,000 visitors to the Tampa-St. Petersburg area, home to well over 4 million people. Over the last few days local authorities have said they could handle the crowds and the approaching storm.