Dr. Haytham Manna.

FLINT — American immigration officials at the Charles de Gaulle Airport in Paris denied Syrian opposition activist Dr. Haytham Manna entry into the United States, even though his visa that does not expire until 2017.

Manna was scheduled to appear on Wednesday on a panel discussion about the Syrian crisis at the University of Michigan- Flint. The discussion, which was to include The Arab American News Publisher Osama Siblani, did not take place. 

Mona Sahouri, the executive director of the Arab American Heritage Council, which was organizing the event, announced the postponement of the discussion on Tuesday via Facebook. She said it would be rescheduled.

Manna, a medical doctor and human rights activist, is the former head of the National Coordination Committee for Democratic Change, which calls for toppling the government but opposes foreign intervention and the militarization of the conflict in Syria.

Syrian opposition supporters have called for the cancelation of the panel, because it has no representatives of the Syrian National Coalition opposition group.

Manna, who lives in France, told Arabic London-based newspaper Rai Lyoum that he was shocked at the decision to deny him entry because an official in the U.S. embassy in Paris had welcomed his visit a few days earlier.

According to Rai Lyoum, the U.S. Embassy in Paris later apologized to Manna and informed him that he was denied entry because all Syrian opposition representatives have to formally notify the U.S. embassy where they live before visiting the United States.