Sen. Elizabeth Warren (D., Mass.), in green, joined fellow Senate Democrats for a news conference at the Supreme Court in Washington on March 17. Ms. Warren, Sen. Cory Booker (D., N.J.) and Labor Secretary Thomas Perez are expected to attend the April 6 unveiling of the Obama administration’s ‘fiduciary rule’ on financial advisers in Washington. PHOTO: CHIP SOMODEVILLA/GETTY IMAGES

WASHINGTON—The Obama administration is set to unveil a final rule next Wednesday that will impose new limits on how brokers offer financial advice to people saving for retirement, according to people familiar with the matter.

Supporters of the “fiduciary rule,” including Sen. Elizabeth Warren (D., Mass.) and Labor Secretary Thomas Perez, plan to announce the landmark regulation at 11:30 a.m. at the Center for American Progress, a think tank closely allied with the Obama administration, the people said. Sen. Cory Booker (D., N.J.) also is expected to join the group, the people said.

The rule, originating from the U.S. Department of Labor, has drawn stiff opposition from Wall Street because it could reshape how brokers earn commissions and restrict their ability to sell some higher-fee products. It requires brokers to act as “fiduciaries,” offering financial advice in their clients’ “best interest.” That contrasts with current rules requiring they only offer “suitable” advice, which critics say allows for biased guidance and conflicts of interest.

The Labor Department and some of President Barack Obama’s closest economic advisers have said the current standard for financial advice costs investors as much as $17 billion a year.

The regulation’s final details will be closely parsed by brokerage firms and insurance companies that could sue to try to block it from taking effect. The American Council of Life Insurers has retained a law firm and is gathering evidence in advance of an expected court battle, according to an internal memo obtained by The Wall Street Journal.