Bill Gates and Warren Buffett will issue a public explanation for the purpose of their trip to China this month following reports that some wealthy people invited to a planned private gathering had declined for fear that they would be asked on the spot to give to charity, Bloomberg and the Telegraph, a British newspaper report.

The two philanthropists will release a letter as early as this week spelling out why they have asked Chinese billionaires to join them at the September 29 dinner.

A spokesman for the Bill and Melinda Gates Foundation said the China meeting was originally scheduled to take place in March, before Mr. Buffett and Mr. Gates embarked on their Giving Pledge campaign to persuade billionaires to pledge at least half their fortunes to charity.

The spokesman said the letter will seek to reassure people that the dinner is not a fund-raising event but an opportunity to “get to know” each other, adding, “We understand the U.S. charity model will not suit China.”