An African trade summit held last week in California had no African delegates after the United States denied them visas to enter the country.

Roughly 60 to 100 Africans delegates, including speakers and government officials from Nigeria, Cameroon, Angola, Ethiopia, Sierra Leone, Guinea, Ghana, South Africa and more, had their requests for visas rejected, said summit organizer Mary Flowers.

The African Global Economic and Development Summit is a three-day conference at the University of Southern California. Typically, delegations from across Africa attend to meet with U.S. business leaders in an effort to foster partnerships.

But this year, every single African citizen who requested a visa was rejected, said Ms. Flowers, CEO of Global Green Development Group, which does economic development work in Africa.

Some are now questioning whether the denials to attend the Los Angeles event are tied to President Trump’s anti-immigration policies. The president is pushing forward with a travel ban against six Muslim-majority countries despite ongoing legal challenges.

The ban covers Somalia, Sudan and Libya in Africa, and citizens from those countries did not seek visas for the event, Ms. Flowers said.

“This conference puts Americans in touch with real people so they can do real business. It’s designed to bring Africa to America’s doorstep for investments and trade,” said Ms. Flowers, who is working on a power plant project in Nigeria with a collaboration that resulted from a past trade summit.

The summit went on as planned March 16 through 18, she said, though with a much smaller group.

“I don’t know if it’s Trump or if it’s the fact that the embassies that have been discriminating for a long time see this as an opportunity, because of talk of the travel ban, to blatantly reject everyone,” Ms. Flowers said this week. “These trade links create jobs for both America and Africa. It’s unbelievable what’s going on.”

A U.S. State Department spokesperson declined to comment, saying in a statement: “We cannot speculate on whether someone may or may not be eligible for a visa, nor on any possible limitations … Applications are refused if an applicant is found ineligible under the Immigration and Nationality Act or other provisions of U.S. law.”

The visa denials may have jeopardized new trade links and business partnerships between U.S. entrepreneurs and African nations, said Ms. Flowers, who also represents Southern California as a member of the District Export Council, a trade group affiliated with the U.S. Department of Commerce.

“We can’t have the government telling us to go do business with Africa and then you slam the doors in their face,” she added, noting that President Trump has been in contact with Nigeria’s president. “We can’t survive as an internal country. We have to operate globally or we won’t be powerful.”

The problems for the trade summit mark the latest example of restricted travel to the United States under President Trump, whose controversial immigration policies and rhetoric have impacted a wide range of industries and communities. Soccer players, musicians, doctors, tech workers, protesters and others from across the globe have been denied entry into the United States, which also has experienced a slump in tourism since President Trump’s inauguration.

Ms. Flowers, who has been organizing the annual summit since 2013, said roughly 40 percent of Africans have been denied visas to attend the event in the past. “But this year it was 100 percent. Every delegation” from Africa, she said. “It was sad to see because these people were so disheartened.”

As a result, the summit had only 50 to 75 participants total, instead of the 150 to 200 who usually attend, she said.

“Financially, that’s a gaping hole — a whole bunch of people who would have contributed not just to the event and to USC, but to the city around.”

She said many of the applicants who were rejected had registered for the event and paid initial visa fees, but then were denied after short interviews, even when they brought extensive documentation, such as bank statements and property records.

Since the rejection, Ms. Flowers has been in contact with U.S. Rep. Karen Bass, a member of the Congressional Black Caucus who represents Los Angeles. Rep. Bass also is the ranking member of the Africa subcommittee.

“When restrictive policies and practices are followed by U.S. embassies when granting visas to Africans, it can hurt opportunities between U.S. and African business entities,” Rep. Bass said in a statement.

“I encourage the State Department to make sure these policies are flexible enough to encourage the free flow of business ideas and opportunities.”