The long-awaited dedication of a US national memorial to slain civil rights icon Martin Luther King scheduled for this weekend has been delayed due to Hurricane Irene, organizers have said. The dedication -- slated for Sunday, the 48th anniversary of King's "I Have a Dream" speech -- will instead take place in September or October, said Harry Johnson, head of the memorial project. "It is with a heavy heart and enormous disappointment that we announce that, in the interest of public safety, we are forced to change our plans," Johnson told a news conference. Johnson said that the dedication would be "moved to a date yet to be determined in September or October." "There are so many individuals who worked tirelessly to dedicate the dream, and make this memorial a reality," he said. The 28-foot (nearly nine-meter) "Stone of Hope" statue is a white granite likeness of King gazing off into the horizon, his arms folded. Designed by Chinese artist Lei Yixin, the memorial cost $120 million. Visitors enter through the Mountain of Despair, a huge boulder symbolizing African Americans' struggle for peace and equality. "In the words of Dr. King, we must accept the finite disappointment but never lose infinite hope. With that in mind, let's remember the spirit of the memorial -- justice, democracy, hope and love," Johnson said. Hurricane Irene is scheduled to hit the US East Coast on Saturday, slamming into North Carolina before heading north toward major population centers including New York City. While Washington is further inland than a number of other cities, rail operator Amtrak has called off train service between the US capital and the South, and a number of coastal communities are already being evacuated. President Barack Obama, the first African American US leader, had been scheduled to speak at the dedication on Sunday, a day after ending his vacation on Martha's Vineyard in Massachusetts. Organizers of the King memorial will still mark the anniversary of the "I Have a Dream" speech with an inter-faith prayer service on Saturday in Washington, Johnson said. The prayer service also saw changes as it was originally scheduled to take place at the National Cathedral, which suffered damage during a rare earthquake on Tuesday. The prayer service will now be held at the Basilica of the National Shrine of the Immaculate Conception, which is the largest Roman Catholic church in North America.