WASHINGTON — In a meeting at the White House with business leaders two weeks into his presidency, Donald J. Trump turned to Jamie Dimon, the chief executive of JPMorgan Chase.

Aren’t the Chinese manipulating their currency? Mr. Trump asked, according to two people who were there.

“No, Mr. President, they’re not,” Mr. Dimon replied. “I think they’re trying to be responsible.”

Others at the meeting, including the former Boeing chief W. James McNerney, agreed. Their advice echoed arguments by members of Mr. Trump’s staff and cabinet that he should abandon his campaign pledge to punish China over its currency.

Mr. Trump was listening. Two months later, facing a strengthened United States dollar and the need for Chinese support against a pugilistic North Korea, he reversed his position.

The meeting with Mr. Dimon and other corporate executives was just one of dozens of sessions Mr. Trump has convened with top businesspeople since becoming president. Nearly 300 executives have visited the White House this year, according to a New York Times tabulation, an open-door policy that is a sharp break with the Obama administration and puts corporate chieftains on par with senior lawmakers in the pecking order of who has influence in Washington.

Frank and occasionally confrontational, the conversations have become a defining feature of Mr. Trump’s young presidency, inspiring policy debates and in some instances 180-degree shifts by the president, according to White House officials and executives who have participated in the discussions.

And while some Democrats and other critics complain business leaders are being granted unfettered access to Mr. Trump — who ran as a businessman planning to apply executive principles to Washington’s problems — the White House is unapologetic. The relationship-building is acting as a welcome substitute for a lack of legislative accomplishments, and presidential aides suggest the rapport positions Mr. Trump for future success.

“The whole idea is, do something with all of this communication and feedback,” said Chris Liddell, the president’s assistant for strategic initiatives and a former chief financial officer at Microsoft and General Motors. “And some of that happened in the first hundred days, but we’re really setting ourselves up for the next thousand days.”

Many executives said that they were rarely given face time with President Barack Obama, and that even when they were, they sensed he wasn’t fully engaged. “The feedback from the Obama White House was, ‘We’ll listen to what you have to say, but we know what we’re doing,’” said Kathryn Wylde, president and chief executive of the Partnership for New York City, a business group.

The parade of chief executives has included familiar Republican faces, like Stephen Schwarzman of Blackstone and Jack Welch, the former chairman and chief executive of General Electric.

But it has also included Democrats. Larry Fink, the chief of BlackRock, was a potential Treasury secretary had Hillary Clinton won the presidency; on Friday, he blasted the administration’s approach to immigration and cast doubt on the economic models underpinning its proposed tax cuts, saying, “There is a lot of uncertainty due to the new administration.”

Eric Schmidt, the executive chairman of Google’s parent company, Alphabet, was a Clinton supporter who predicted in January that Mr. Trump would do “evil things” as president. And Charles Phillips, chief executive of the software company Infor, sat on Mr. Obama’s Economic Recovery Advisory Board.

“As he’s shaping his view, he is kind of learning a lot of things,” Mr. Phillips said of Mr. Trump. “So this is a good time, in this first six months, to go in there.”

Alcoa’s chief executive, Roy Harvey, experienced that firsthand on Thursday, as he watched Mr. Trump sign a memorandum directing the Commerce Department to investigate the effects of aluminum imports on national security.

“We appreciate the support of the administration to try to make a level playing field,” Mr. Harvey said.

Mr. Trump’s dialogue with business leaders has at times been freewheeling, and at times focused on topics that were first dissected in small sessions with staff or cabinet members. At the gatherings, some executives, who have been cowed by the president’s itchy Twitter finger and tendency to take quick offense to perceived slights, have found Mr. Trump open to disagreement.

At the meeting when the Chinese currency was discussed, Elon Musk, the South African-born chief of Tesla and SpaceX, attacked a newly signed executive order banning travel and immigration from seven predominantly Muslim countries. Not only did Mr. Trump welcome the criticism, said the people who were present, he calmly defended his position, noting that public-opinion polls supported his viewpoint before sharing the floor with John F. Kelly, the Homeland Security secretary.

Some business leaders have parlayed their White House access into support for specific causes. In a TED talk on Friday, Mr. Musk said, “I’ve used the meetings I’ve had to argue in favor of immigration and climate change,” according to a Twitter post published by the organization. Mr. Schwarzman of Blackstone encouraged Mr. Trump to soften his hard-line stance on deporting so-called Dreamers — the young, undocumented foreigners living in the United States.

Late last year, IBM’s chief executive, Ginni Rometty, wrote a letter to the president-elect, urging him to expand vocational job-training programs. That idea, which she later repeated directly to the president at the White House, was integral to a meeting Mr. Trump called with Chancellor Angela Merkel of Germany and several multinational companies. Mr. Phillips of Infor also raised the subject of job training.

“Because of these conversations, it really became a significant focus of the administration,” said Reed Cordish, assistant to the president for intergovernmental and technology initiatives.

Executives are hoping the White House will support putting federal education grants toward skills-training programs rather than just traditional college. So far, however, the administration hasn’t taken a public stance on the legislative efforts to do so.

Mr. Trump’s unofficial business cabinet was handpicked, in many cases, by influential companies and trade associations. On the president’s first full weekday in office, he welcomed a dozen industrial executives who had been convened by Andrew Liveris, head of the Dow Chemical Company. A senior staff member at the Retail Industry Leaders Association put together a panel of executives drawn from her group’s ranks.

Mr. Schwarzman recruited a range of business leaders, economists and policy experts for the president’s strategic and policy forum, which regularly meets at the White House and has emerged as the most elite outside counsel.

To be invited to the policy forum, there were a few criteria, according to someone who was briefed on the selection process: Be an expert in your field who is respected by Mr. Schwarzman, be a United States citizen and don’t be vetoed by Mr. Trump.

The task of dealing day to day with the chief executives falls largely to Mr. Liddell, a New Zealander by birth, and Mr. Cordish, a Baltimore real estate scion, who share a cramped office in the West Wing. It is decorated with a laminated United States map and a full-page ad, ripped from The Wall Street Journal, that thanks Mr. Trump for agreeing to reconsider fuel-economy standards. It was purchased by auto trade groups.

During a recent interview, Mr. Liddell and Mr. Cordish were upbeat. Since the White House “listening groups” began, Mr. Cordish said, they’ve been barraged with ideas from executives and trade groups for deregulation, job creation and the streamlining of services.

In a meeting in early April, a group of 50 or so chief executives involved with the Partnership for New York City proposed adding public housing to Mr. Trump’s infrastructure initiative. The idea was recirculated at another trade group meeting about a week later, suggesting that the White House was seriously considering it.

Some of the infrastructure changes under consideration would improve the government’s own inner workings, including at the White House itself. “A lot of technology here is 20 years out of date,” Mr. Liddell said.

But even with all the access, some chief executives are frustrated with what they describe as well-intentioned but so far fruitless talk — and a public environment that can be leery of any cooperation with the Trump administration.

Robert Hoopes, a consultant who advises nonprofit groups and large companies and has done work for prominent Democrats, including former Vice President Joseph R. Biden Jr., said executives were making a careful calculation when they traveled to Pennsylvania Avenue. If the topic for discussion is core to your business, Mr. Hoopes said, “you want to be a part of that conversation.” But if the session is peripheral or unrelated to your business, he said, the “risk calibration” is very different.

Two dozen trade-group officials and chief executives, some of them suggested as potential interview subjects by the White House, either refused to speak for this article or didn’t respond to messages. Others declined to be quoted on the record, citing the toxic environment and the potential fallout among the public and their own employees for being regarded as an ally of Mr. Trump.

“Usually, when a campaign is over, things settle down and people feel they can work with the president without having a backlash,” Ms. Wylde of the Partnership for New York City said. “In this case, there continue to be divisive forces that don’t want that to happen.” C.E.O.s, she said, “feel pressure from all sides.”