WASHINGTON (Reuters) - Wall Street's top regulator is set to approve new rule changes on Wednesday that require mutual funds and exchange-traded funds to report portfolio holdings on a monthly basis rather than four times a year, bringing greater transparency to investors, officials said.

The five-member U.S. Securities and Exchange Commission is due to hold a public meeting at 10:00 am Wednesday. However, in a retreat from earlier plans, the agency will not consider more substantial proposed "swing pricing" regulations which have faced stiff industry opposition.

The SEC is due to instead limit guidance to complying with existing, related regulations that govern how "open-end" funds manage liquidity risk, SEC officials told reporters in advance of the vote. In such funds, investors may redeem their shares on a daily basis.

The swing pricing proposal aimed to help open-end funds better withstand market stresses, like those seen at the start of the coronavirus pandemic, by shifting the costs of hasty redemptions to those who cash out rather than those who remain in the fund. The agency disclosed last month that it expects to re-draft the proposal.

Under current reporting rules, registered investment management companies are required to file quarterly reports on portfolio holdings with the commission 60 days after the close of each quarter. But investors only gain access to data that cover the third month of the quarter.

Under the rule amendments due to be considered Wednesday, the same funds would be required to file those reports within 30 days of the end of each month, with each such report becoming public after a further 30 days.

The improved transparency will help investors make decisions and promote analysis by third parties, according to the SEC.

If adopted, the regulations are set to take effect in November next year or May of 2026 for funds with net assets of $1 billion or less.

The guidance due to be considered on Wednesday will also address questions and concerns the agency became aware of through outreach and monitoring of markets, SEC officials said.

These include how frequently open-end funds classify their assets' liquidity, meaning how readily they can be sold for cash, the meaning of the word "cash" as it's used in the regulation, and reviewing required minimums for highly liquid investments.