The real estate magnate takes office next month after promising to repeal outgoing President Barack Obama's signature healthcare policy which helped millions more Americans get medical insurance but has been a target of Republican attacks.

Agnes Soucat, the WHO's director of health system governance and financing, said there were various ways of providing health cover to more people, and it amounted to "political choices."

"We as the WHO really encourage the new administration to make sure that the social contract is expanded and that all U.S. citizens have access to health care," Soucat told a news briefing in Geneva.

The United States is the only country among the 35 member states of the Organisation for Economic Cooperation and Development (OECD) not to provide universal health care, a key U.N. Sustainable Development Goal for 2030, she said.

The Affordable Care Act, known commonly as Obamacare, has provided some 25 million previously uninsured Americans with health cover. Republicans say it has created unwarranted government intervention in personal healthcare and private industry.

Trump in late November picked Republican U.S. Representative Tom Price, an orthopedic surgeon from Georgia and Obamacare critic, to be his health secretary.

Price has long championed a plan of tax credits, expanded health savings accounts, and lawsuit reforms to replace Obamacare.

Republicans are divided over how quickly an Obamacare repeal should go into effect, with some saying a delay would give them time to work on a replacement, instead of throwing millions of Americans out of their health insurance with no substitute.

"There are different strategies to make universal health care particularly pro-poor," Soucat said. "So what we are saying is, yes, this would be a setback if people would lose coverage."

(Reporting by Stephanie Nebehay; editing by Richard Lough)