NEW YORK/WASHINGTON—The New York Stock Exchange has started the process of delisting securities of three Chinese telecom companies, after President Donald Trump last year barred U.S. investments in Chinese firms that Washington says are owned or controlled by the military. The move by the NYSE, which will limit U.S. investor access, follows global index providers MSCI Inc., S&P Dow Jones Indices, and FTSE Russell and Nasdaq deleting various Chinese companies from their indexes. It’s “a modest step, but at least an awakening to national security and human rights-related risk,” said Roger Robinson, a former White House official who supports curbing Chinese access to U.S. investors. NYSE said that the issuers, China Telecom Corporation Ltd., China Mobile Ltd., and China Unicom (Hong Kong) Ltd., were no longer suitable for listing as the order prohibits any transactions in securities “designed to provide investment exposure to such securities, of any Communist Chinese military …