This weekend, more than 50,000 American Muslims are expected in Chicago for an annual gathering.

But they won’t all be attending the same meeting.

American blacks and immigrant Muslims are holding separate conventions just three miles apart — underscoring the divide between the two groups that Muslim leaders have been struggling to bridge for years.

The split is a significant — and highly sensitive — Muslim issue. Islam teaches unity among all believers, and American blacks comprise about 30 percent of observant Muslims in the United States.

Leaders on both sides say they can ill afford rifts within their community as the war on terrorism enters its third year. American Muslims have been striving to present a positive image of their religion and protect their civil rights under intense scrutiny by law enforcement.

“We’re different culturally and we’re different ethnically and that creates some difficulties in terms of communication and understanding,” said Imam Earl Abdulmalik Mohammed, a national representative of black Muslim leader Imam W. Deen Mohammed of the American Society of Muslims.

Sayyid M. Syeed, secretary general of the Islamic Society of North America, which was founded by immigrants, said the two groups enjoy “total comfort and cooperation,” regardless of the separate conventions.

Participants in the American Society of Muslims convention will automatically be registered at the Islamic Society meeting, Syeed said. Leaders will also visit each others’ assemblies, which both started Friday.

However, Abdulmalik Mohammed said that “it’s a matter of concern” that no joint events have been scheduled.

Many efforts have been made to improve relations between immigrant and black Muslims, but deep differences remain, rooted partly in how Islam spread among American blacks.

Most came to the religion through black nationalist movements and the Nation of Islam, which had taught that its founder, Wallace D. Fard, had divine status and his successor, Elijah Muhammad, was a prophet. Mainstream Islam teaches that there is only one God and no prophets came after Muhammad. For that and other reasons, many immigrant Muslims consider the Nation of Islam a cult.

But Imam W. Deen Mohammed, the son of Elijah Muhammad, transformed the movement after taking it over in the 1970s. He gradually moved his thousands of followers toward mainstream Islam, while Louis Farrakhan revived the old Nation of Islam under his leadership.

“Through the ’60s and into the ’70s, there was practically no relationship,” between immigrants and blacks, said Ishan Bagby, a University of Kentucky professor who is black and a convert to Islam. “Really, the ’80s was the beginning of a relationship.”

Bagby was among a handful of blacks asked to serve in leadership positions in national immigrant Muslim organizations to help build connections between the two groups. However, closer ties served to highlight their communities’ dramatically different needs.

Immigrant Muslims tend to be wealthier professionals who live and worship in the suburbs, while mosques affiliated with W. Deen Mohammed are mainly urban, serving middle-class or lower-income blacks.

Black Muslims, who tend to vote Democrat, said they felt alienated in 2000 when leaders of the immigrant community made their first unified endorsement of a presidential candidate, Republican George W. Bush.

Racism has been another obstacle.

Many immigrants arrived in the United States with a warped view of blacks as unsophisticated and even dangerous, and failed to understand the discrimination they faced, leaders for both groups say.