March 4 (Reuters) - President Joe Biden's administration on Monday urged a U.S. appeals court to preserve a federal mandate that requires health insurers to cover preventive care services including HIV-preventing medication and cancer screenings at no extra cost to patients.

"These are preventive services provisions that are critical and life-saving to millions of Americans," Daniel Aguilar, a lawyer for the government, told a three-judge panel of the New Orleans-based 5th U.S. Circuit Court of Appeals during arguments in the administration's appeal.

The administration is asking the 5th Circuit to overturn a federal judge's ruling that, if allowed to take full effect, would strike down the mandate that insurers cover a wide range of services chosen by a federal task force without co-pays. The mandate is part of the 2010 Affordable Care Act (ACA), often called Obamacare because it was championed by then-President Barack Obama.

The judges during the arguments did not clearly signal how they would rule.

The PrEP drugs approved in the United States to prevent HIV infection, which can cause AIDS, are made by Gilead Sciences and by ViiV Healthcare, a joint venture of GSK, Pfizer and Shionogi.

A group of businesses led by Texas-based Christian wellness center operator Braidwood Management in 2020 sued over the mandate. While they brought their case because they objected on religious grounds to covering HIV pre-exposure prophylaxis (PrEP), they argued that the entire mandate violated the U.S. Constitution because it gave too much power to a task force chosen by a mid-level U.S. health official, rather than appointed by the president and confirmed by the Senate.

U.S. District Judge Reed O'Connor in Fort Worth in March 2023 agreed and blocked enforcement of the preventive care mandate nationwide.

Jonathan Mitchell, a lawyer for Braidwood, argued that the 5th Circuit should uphold that conclusion.

"The individuals who wield these powers to impose compulsory preventive care coverage mandates on private insurers hold sufficient authority to make them into officers of the United States," Mitchell said.

The Biden administration has argued that U.S. Secretary of Health and Human Services Xavier Becerra, who was confirmed by the Senate, can retroactively "ratify" the task force's decisions. Becerra issued a memo in 2022 doing so, but Mitchell argued that the Obamacare law did not allow it.

Aguilar also told the judges on Monday that even if the court agrees with O'Connor's conclusions, it should narrow his order to give the plaintiffs what they wanted while preserving as much of Obamacare as possible - an approach he likened to using a "scalpel" instead of a "sledgehammer."

"Plaintiffs don't have a particular reason to object to somebody in Wisconsin receiving lung cancer screening without cost sharing," Aguilar said.

O'Connor's ruling does not apply to services the task force recommended before the ACA was enacted, including breast cancer screening.

Two members of the 5th Circuit panel, Circuit Judges Don Willett and Cory Wilson, were appointed by Republican former President Donald Trump, and the third, Circuit Judge Irma Carrillo Ramirez, was appointed by Biden, a Democrat.

(Reporting by Brendan Pierson in New York; Editing by Will Dunham and Alexia Garamfalvi)