Donald Trump campaigned for president as a savvy billionaire who would apply his business acumen to improving the U.S. economy, cutting taxes for Americans and negotiating better trade deals.

But his vast, complicated network of businesses under the Trump Organization, including numerous foreign investments and debts, could create unprecedented conflicts of interest when he takes the oath of office as U.S. president in January, government ethics experts said.

Federal law does not prohibit the president from being involved in private business while in office, even though members of Congress and lower-ranking executive branch officials are subject to strict conflict-of-interest rules. Lyndon Johnson, for instance, quietly managed his broadcasting businesses despite insisting publicly that he had ceased all involvement, according to his biographer, Robert Caro.