In the course of his interactions with African leaders, the president unveiled a series of initiatives, including an agreement meant to encourage the formation of a continentwide free-trade zone that has stalled over the last few years. He vowed to help African countries do more to transition to clean energy and plug into the digital economy, a contrast to China, which has focused much of its investment in Africa on building roads, bridges, airports and other physical infrastructure.

Mr. Biden said in his keynote address that the goal was not to “create political obligation or foster dependence” but to “spur shared success,” a phrase he said characterized his approach. “Because when Africa succeeds, the United States succeeds,” he said. “Quite frankly, the whole world succeeds as well.”

The Biden administration has sought to deflect the perception that its efforts this week were aimed at competing with China, which has surpassed the United States in trade and economic cooperation with Africa.

But the emphasis put on Africa was an implicit recognition that the United States has little choice but to commit to the continent, which is projected to account for one in four people by 2050 and is rich in the resources needed to combat climate change and transition to clean energy, like vast forests and rare minerals used to power electric vehicles.

Mr. Biden’s challenge was to convince the African leaders that he was serious about wanting to trade with them. Many were openly skeptical. At a side event in Washington hours before Mr. Biden spoke, President Paul Kagame of Rwanda shrugged when asked if anything had come out of the inaugural U.S.-Africa Leaders Summit hosted by Mr. Obama in 2014.

“Well, at least we had a good meeting,” he replied, drawing laughter from the crowd.

Mr. Biden planned to return to the summit at the Washington Convention Center on Thursday for a session on the African Union’s strategic vision for the continent. Vice President Kamala Harris will host a working lunch, and Mr. Biden will close the gathering with a discussion of food security.

The Covid-19 pandemic and Russia’s invasion of Ukraine provided Mr. Biden with an entry point for his pitch to Africa’s leaders, reminding them that the United States delivered 231 million vaccines to 49 African countries.

Yet the war in Ukraine also underscored the scale of American priorities. A mistake by Mr. Biden in his speech underscored the context. He described a digital economy initiative for Africa as a $350 billion investment, when in fact it will be $350 million, as noted in the official White House transcript correcting the president’s error. By contrast, the Biden administration and Congress have committed $66 billion to the war in Ukraine and the White House has just asked Congress for another $37.7 billion.

Some analysts wondered whether the roster of projects ticked off by the president and his aides this week would be more effective than a single broad initiative like those introduced by Mr. Bush and Mr. Obama.

“When I hear a laundry list, a long list of investments, that’s just showing what the U.S. is doing,” said Aubrey Hruby of the Africa Center at the Atlantic Council. “But I don’t know if that sinks in very well. Whereas with Power Africa it was simpler, perhaps more memorable. It drew on the power of the podium.”

“The key,” she added, “will be what people remember one month from now. Or one year from now. What becomes real.”

The digital economy project includes a partnership with Microsoft and programs to train African entrepreneurs to write code. “American big tech recognizes that the demographic future of this world is African,” Ms. Hruby said. “A million Africans turn 18 every month. This is the future.”

As ever in this week’s summit, China was the unspoken factor. When Mr. Biden announced $800 million in new contracts for Cisco Systems and a smaller company named Cybastion “to protect African countries from cyberthreats,” it offered a counterpoint to the dominance of Huawei, the Chinese technology firm whose cellphones and computers systems are ubiquitous across Africa, stoking fears that Beijing could use them for cyberespionage.

The Biden administration this week announced its support for an initiative to use minerals mined in the Democratic Republic of Congo to make batteries for electric vehicles in factories in neighboring Zambia. That deal meets the African goal of keeping supply chains for one of the world’s hottest new businesses on the continent.

It also meets an American strategic objective, countering worries in Washington that China is obtaining a stranglehold on rare minerals in countries like Congo.

The administration also signed a memorandum of understanding to support the African Continental Free Trade Area, which was started in 2019 and promises to unlock the enormous economic potential of a continent of 1.3 billion people and a total market of $3.4 trillion by easing trade barriers between individual countries.

Africa’s mostly colonial-era borders are further heightened by protectionist policies, poor transport links and other measures that hinder trade. The free-trade area could increase intra-Africa trade by up to one-quarter, or $70 billion, by 2040, helping to lift 30 million people out of extreme poverty, according to the United Nations and the World Bank. But implementation has been slow, and experts say that assistance from the United States and other foreign powers is needed to bolster its chances of success.

Jake Sullivan, Mr. Biden’s national security adviser, said the current administration has been working hard to restore ties to Africa over the nearly two years since Mr. Trump left office.

“Look, any time an administration chooses not to put as much energy or emphasis into a place, it obviously has some ramifications,” he told reporters this week. But “we believe that we are not coming into this summit from a standing start. We’re coming into this summit with a head of steam around a set of issues that this summit, I think, is going to kick into a higher gear.”