President-elect Donald J. Trump is keeping secret the names of the donors who are funding his transition effort, a break from tradition that could make it impossible to see what interest groups, businesses or wealthy people are helping launch his second term.

Mr. Trump has so far declined to sign an agreement with the Biden administration that imposes strict limits on that fund-raising in exchange for up to $7.2 million in federal funds earmarked for the transition. By dodging the agreement, Mr. Trump can raise unlimited amounts of money from unknown donors to pay for the staff, travel and office space involved in preparing to take over the government.

Mr. Trump is the first president-elect to sidestep the restrictions, provoking alarm among ethics experts.

Those seeking to curry favor with the incoming administration now have the opportunity to donate directly to the winning candidate without their names or potential conflicts ever entering the public sphere. And unlike with campaign contributions, foreign nationals are allowed to donate to the transition.

“When the money isn’t disclosed, it’s not clear how much everybody is giving, who is giving it and what they are getting in return for their donations,” said Heath Brown, a professor of public policy at John Jay College of Criminal Justice who studies presidential transitions. “It’s an area where the vast majority of Americans would agree that they want to know who is paying that bill.”

Mr. Trump’s transition team, led by Linda McMahon and Howard Lutnick, both of whom were nominated to cabinet positions last week, has repeatedly said it intends to sign the agreements with the Biden administration, known as memorandums of understanding.