(Reuters) - Top mutual fund manager Vanguard has paused meetings with portfolio companies while it reviews the impact of new guidance on investor activism from the U.S. Securities and Exchange Commission, according to people familiar with the matter.

In a recent notice, the SEC, whose acting chair was appointed by President Donald Trump, revised its "beneficial ownership reporting" interpretations in ways that could put new burdens on firms like Vanguard that now rely on the SEC's Schedule 13G form to report major holdings.

Going forward, the SEC said managers may need to use the more complex Schedule 13D, which would increase their costs, if they pressure management on matters like climate questions or whether a company has a staggered board or poison pill takeover defenses.

Vanguard put the pause in place because it is "trying to process and understand the new guidelines so they can remain a 13G filer and not a 13D filer," said one of the sources, speaking on condition of anonymity.

Ending the meetings could reduce the power of shareholder activists focused on environmental, social or governance questions, corporate attorneys say, the apparent goal of the SEC's current leadership. But it could also diminish the input that executives receive from top investors on more traditional corporate questions like executive pay.

A Vanguard representative did not respond to questions on Tuesday.

Rival asset manager BlackRock had also paused meetings with some of its portfolio companies. A company representative did not immediately comment on the status of these meetings on Tuesday.