The United States put its eastern seaboard on alert for Hurricane Irene Tuesday as the powerful storm barreled up from the Caribbean on a path that could hit the U.S. coast on the weekend.

Even as the first hurricane of the 2011 Atlantic season pounded the Turks and Caicos Islands and the southeast Bahamas with battering winds and rain and dangerous storm surge, coastal residents in Florida and the Carolinas were preparing for Irene's approach.

``I pray God's blessing on us all,'' Bahamas Prime Minister Hubert Ingraham said as he urged residents of his Atlantic archipelago nation southeast of Florida to take shelter.

Irene is the ninth named storm of the busy June-through-November season and looks set to be the first hurricane to hit the United States since Ike pounded the Texas coast in 2008.

It weakened on Tuesday to a Category 1 hurricane on the five-step Saffir Simpson scale of intensity, but could strengthen into a major Category 3 storm with winds over 111 miles per hour by Thursday, the Hurricane Center forecasters said

While warning the entire U.S. East Coast to be on the alert, Federal Emergency Management Agency Administrator Craig Fugate and National Hurricane Center Director Bill Read said it was too early to be certain where Irene would directly hit the coastline.

``We're going to have a very large tropical cyclone move up the Eastern Seaboard over the next five to seven days,'' Read said on a conference call in which he spoke along with Fugate.

The ``best guess'' forecast was that it would approach the coast of the Carolinas Saturday morning as a major storm of Category 3 or upward, Read said.

After that, the already saturated New England region of the East Coast could also be at particular risk for torrential rains, high winds and flooding from Irene, Fugate said. Major eastern cities like Washington and New York could feel some impact from Irene, the forecast indicated.

In a separate development, a magnitude 5.9 earthquake struck the U.S. East Coast, shaking Washington, New York and other cities.

Irene could put a damper on Sunday's dedication ceremony for the new memorial honoring civil rights leader Martin Luther King Jnr. on Washington's National Mall. Tens of thousands of people, including President Barack Obama, were expected to attend.

Forecasts showed Irene posing no threat to U.S. oil and gas installations in the Gulf of Mexico.

 

SALT HARVEST HALTED

Irene was heading west-northwest over the Turks and Caicos Islands and southeastern Bahamas.

At 5 p.m., it had top winds of 90 miles per hour and was centered 110 miles east of Great Inagua Island in the southern Bahamas. Forecasters warned that a storm surge up to 13-feet high could wash over parts of the Bahamas.

Cruise line Royal Caribbean rearranged itineraries for six ships, skipping two scheduled stops at its Coco Cay island in the Bahamas so staff could prepare and evacuate.

Carnival Cruise Lines changed ports of call or shifted the arrival or departure times at ports for seven of its ships, a spokesman said.

Morton Salt shut down its operations on Great Inagua because rain melts the salt cake in its crystallizers, leaving it unable to continue the salt harvest. The company temporarily laid off 100 workers this month after getting more than double the average rainfall in July.

``We are hoping and praying we don't get any more precipitation from this hurricane,'' said Glen Bannister, Morton Salt's managing director.

In North Carolina, where Irene was forecast to come ashore on Saturday, Governor Bev Perdue urged residents to make sure they had three days worth of food, water and supplies.

``You may lose water or electrical power during the storm, and grocery stores and other businesses may be closed. Also make sure you know the evacuation routes,'' Perdue said.

Evacuations were to begin on Wednesday for parts of North Carolina's Outer Banks, the stretch of barrier islands and beaches jutting into the Atlantic Ocean. Tourists were ordered to leave some areas.

At a hardware store in Charleston, South Carolina, Carlito Resnicki, 29, hauled sheets of plywood to his car to board up his home. ``I have a wife. ... Mama Bear said go buy plywood, so I came.''

Irene could still swing farther east away from the U.S. coast. But if it skirts North Carolina's Outer Banks without weakening and then plows northward through the heavily populated mid-Atlantic and New England coasts as a Category 1 or 2 hurricane, ``It could become one of the ten most damaging hurricanes in history,'' hurricane expert Jeff Masters of private forecaster Weather Underground wrote in his blog.

Obama was briefed about Irene while on vacation at the Massachusetts island of Martha's Vineyard. He signed an emergency declaration Monday for Puerto Rico after the storm pummeled the U.S. territory with heavy rains and winds. Puerto Rican authorities reported power outages and some flooding, but there were no reports of deaths or injuries. (Additional reporting by Manuel Jimenez in Santo Domingo, Jane Sutton and Tom Brown in Miami, Harriet McLeod in Charleston, S.C., Barbara Liston in Orlando; Writing by Pascal Fletcher; Editing by Christopher Wilson)