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Six days before Donald Trump is set to announce a plan to exit operations of his company, former Republican officials and a conservative author who targeted the Clintons — and has close ties to a top Trump adviser — signed a letter urging the president-elect to put his business enterprises into a blind trust in order to avoid any suggestion that his decisions benefit him, a watchdog group said.

"We believe you need to act now to ensure that as president you will not have conflicts of interests or the appearance of such conflicts," says the letter, which Citizens for Responsibility and Ethics in Washington helped organize.

The signers include former New Jersey Gov. Christine Todd Whitman, former Minnesota Gov. Arne Carlson, former Rhode Island Rep. Claudine Schneider — all Republicans — and "Clinton Cash" author Peter Schweizer, according to CREW.

"Ethics and conflict of interest rules and norms are not partisan or ideological issues," the letter says. "It has long been understood that these are safeguards to protect the integrity and credibility of government decisions and actions, and the interests of the American people."

Some Republicans have expressed concerns that Trump's holdings could subject him to ongoing questions over conflicts of interest. Richard Painter, a former top ethics lawyer to President George W. Bush who was recently named to CREW's board, has been one of the few prominent Republicans to join Democrats and ethics experts calling for a complete divestment by Trump and his family.

Schweizer's participation is notable after his research helped focus scrutiny on Hillary Clinton and her family's foundation, a topic that dogged her through most of her unsuccessful campaign. Schweizer has ties to Stephen Bannon, who left Breitbart News to become CEO of Trump's campaign and will serve as White House chief strategist and senior counselor. The pair turned "Clinton Cash" into a movie.

Schweizer also researched former Florida Gov. Jeb Bush, who briefly sought the 2016 Republican nomination.

Trump has assets and debts connecting him to businesses and governments around the world. Trump has said he will have a news conference Dec. 15 to discuss his plan to remove himself from business operations "in total."