DAKAR, Senegal — President Barack Obama opened a weeklong trek to Africa on Thursday with a sales pitch, stressing the urgent need for U.S. companies to invest everything and anything they can in the up-and-coming economies in Africa.

“The reason I came to Africa is because Africa is rising,” Obama said at a news conference alongside Senegal President Macky Sall. “And it is in the United States’ interests … to deepen and broaden the partnerships and potential here. This is going to be a continent that is on the move. … And there’s a reason why a lot of other countries around the world are spending a lot of time here.”

To prove his point, he mentioned the looming competition from China. There was no need.

Africans have seen firsthand China’s intense interest in their continent, including Senegal, the French-speaking nation that is the first stop of Obama’s three-nation trip to the continent. Across Africa, the United States already finds itself playing catch-up with China.

China overtook the U.S. as Africa’s largest trading partner years ago. It has helped pay for roads and bridges and bought 20 percent of Standard Bank of South Africa. Its president and vice president have visited more than 30 African countries in recent years, with President Xi Jinping putting Africa on the itinerary of his first trip after his ascension to leader. Obama’s trip is his first multiday visit to sub-Saharan Africa in more than four years in office. His only other stop was in Ghana for about 20 hours on his way home from Europe.

In Senegal, Obama focused on a variety of issues, including democracy. But his main message was about trade and investment. He said the United States is moving from merely providing aid to Africa to partnering on investments in infrastructure and technology, in part through a renewed and improved African Growth and Opportunity Act.

Large, enthusiastic crowds greeted Obama on his first day in Africa, with some spectators lining the streets to catch a glimpse hours before he even departed his hotel. Local newspapers were filled with articles and ads, some urging Obama to keep sending money to combat AIDS/HIV. Thousands of American flags and posters, large and small, welcomed the first black U.S. president to the continent where his father was born. “Welcome home, President Obama” one sign read. “We hope you enjoy your stay.”

In the streets of the capital city, though, local residents asked for something more durable from the visit.

“We don’t want money,” said Laye Mamelaye, 48, a self-employed tour guide who was born and raised in Senegal. “We want more business.”

Obama was joined on the trip by members of his economic team — U.S. Trade Representative Mike Froman and officials from the Export-Import Bank and the U.S. Agency for International Development.

Some business leaders were disappointed that private companies did not have a more visible active role on the Africa visit.

The U.S. Chamber of Commerce, which is often along on presidential trips overseas, does not have an official business entourage on this trip despite making Africa a priority.

“Is it unusual? No. Do we wish that it happened? I think it would have been advantageous,” said Scott Eisner, vice president of African affairs for the influential chamber.

The chamber, fairly new to Africa, sees potential in South Africa first and foremost, but also Kenya, Ghana, Ethiopia and Mozambique. Eisner withheld judgment on the wisdom of a trip without a business entourage, hoping to hear details of the public-private partnerships Obama has envisioned for power generation.

White House officials said they invited dozens of business leaders from the United States as well as Asia and Europe to attend different events, including those about food security in Senegal and electricity in Tanzania. “What we hear from our businesses is that they want to get in the game in Africa,” said Ben Rhodes, a deputy national security adviser to the president.

Also Thursday, Obama met with Sall behind closed doors before visiting Goree Island, the western point in the continent where slaves were shipped to North America. He stood quietly alone in the doorway of the former slave house facing the Atlantic Ocean, called the Door of No Return, before he was joined by his wife, Michelle, and their daughters, Sasha and Malia.

Obama is scheduled to depart Senegal today for South Africa, but the fragile condition of Nelson Mandela, the ailing former president and anti-apartheid leader, threatens to complicate his trip to Pretoria and Cape Town.

Mandela’s condition said to be stable

JOHANNESBURG — South Africans held their collective breath over the fate of Nelson Mandela on Thursday as a stormy mix of rumor and official reports deepened concerns over his health, although by day’s end the president’s office said Mandela’s condition had stabilized.

Although the government noted a deterioration in Mandela’s condition Wednesday night, President Jacob Zuma offered modest reassurance after a visit Thursday morning, relaying medical reports that Mandela, 94 and still critically ill, was “now stable.”

But worries are deepening as South African leaders prepared to welcome President Barack Obama today.

Mandela has long been a beacon for Obama, who recounted again Thursday how the revolution unleashed by Mandela a world away had inspired his own activism.

— From wire reports