Last week, Mr. Guterres appointed a new special representative for the Haiti cholera crisis — the third one so far — to devise new fund-raising solutions.

And on Friday, United Nations officials were served with a reminder that their effort to shield the organization from Haiti cholera lawsuits by asserting diplomatic immunity might not necessarily work. In papers filed in Federal District Court in Brooklyn, the lead lawyer for Haitian victims challenged a request for dismissal of their case by the Justice Department, which acted on behalf of the United Nations.

The arguments by the lead lawyer, James F. Haggerty, differed from those in a separate lawsuit filed by the Institute for Justice and Democracy in Haiti, an advocacy group, which argued that the United Nations had failed to give victims a way to settle their grievances. A federal appeals court dismissed that suit last August at the Justice Department’s request.

The Justice Department has until July 7 to respond to Mr. Haggerty’s filing, which argues that the United Nations established as far back as the 1990s that it was legally liable for damages caused by negligence from peacekeeping operations.

Acceptance of that liability, Mr. Haggerty said, was the same as waiving immunity under the treaty the United Nations has invoked as protection, known as the Convention on the Privileges and Immunities of the United Nations.