California has sued a prominent children’s hospital system to prevent it from ending gender-related treatments for transgender young people.

Amid a broader push by the Trump administration to block such care, California’s action appears to be the first time a state has sued a health care provider to force it to continue, legal experts said.

In the lawsuit, Rob Bonta, California’s attorney general, argued that Rady Children’s Health, the state’s largest pediatric health system, had violated a legal agreement with the state by unilaterally deciding to stop providing hormone treatment and other gender-related health care to transgender patients under the age of 19.

The care was scheduled to end on Friday and would have affected about 1,450 patients, the lawsuit said. A San Diego County Superior Court judge on Thursday ordered Rady Children’s to keep offering the care until Feb. 10, when he planned to decide whether the hospital must continue the services while the case proceeds, according to Mr. Bonta’s office.

The state’s suit, which was filed last week, said that when the attorney general’s office approved Rady’s deal to merge with Children’s Hospital of Orange County in 2024, the hospital system was required to keep providing the same level of specialty health care, including gender-related care, through 2034.

Instead, the lawsuit said, Rady Children’s gradually began curtailing treatment for transgender young people, such as by declining to accept new patients, before telling existing transgender youth patients that the system would no longer provide them with gender-related care.