Maya Soetoro-Ng is scheduled to speak at a spiritual rally Sunday meant to bring together African-Americans in support of her half-brother Barack Obama's presidential bid. AP library photo | May 2007

Soetoro-Ng also will read a letter sent from Obama to the crowd, organizer Bettye Jo Harris said Tuesday.

"Because of the diversity of these Islands, we can be a leader in showing other parts of the country we are unified," Harris said.

The rally is expected to draw 300 people to Trinity Missionary Baptist Church at 4 p.m., Harris said. The church is near Hickam at 3950 Paine Circle.

There are fewer than 40,000 African-Americans in Hawai'i, including those in the military, according to the 2000 U.S. Census.