The United States had threatened to slap 25 percent tariffs on auto exports from Japan but Washington agreed not to do so while fresh trade talks are underway.
The sources cautioned that there was always a chance that the negotiations could collapse at the last minute and asked not to be identified because the matter is confidential.
With its Saudi ties causing jitters, SoftBank selling is "more psychological than anything related to worries on its fundamentals," said Makoto Kikuchi, chief executive of Myojo Asset Management.
Ma did not say when the Jack Ma Institute of Entrepreneurs would launch, but said the aim was to train 1,000 tech leaders a year over the next 10 years.
US president Donald Trump and Japanese PM Shinzo Abe agreed in September to start trade talks in an arrangement that, for now, protects Japanese automakers from further tariffs.
Tokyo hopes other countries would join Japan to counter U.S. President Donald Trump's focus on narrowing U.S. trade deficits through purely bilateral trade deals.
The market ructions have now cascaded through to developed markets with Wall Street extending a slide into a sixth session on Thursday amid the trade war fears.
The Monetary Authority of Singapore (MAS) said it would slightly increase the slope of the Singapore dollar's policy band, as predicted in a Reuters poll.
The luxury carmaker said on Thursday it would increase its stake in its venture with Brilliance China Automotive Holdings Ltd to 75 percent from 50 percent.
The global plunge erased hundreds of billions of dollars of wealth. The head of the International Monetary Fund said stock market valuations have been "extremely high".