The White House had asked the Supreme Court to intervene after lower courts prohibited Trump's administration from implementing controversial restrictions on transgender service.

The administration said there is "too great a risk to military effectiveness and lethality" to allow transgender people to serve openly -- a policy enacted under Trump's predecessor Barack Obama.

The court decided by a narrow 5-4 majority to suspend prohibitions restricting transgender service as litigation moves forward in lower courts.

Under the Obama-era policy, transgender recruits were to start being accepted by July 1, 2017. The Trump administration postponed that date to January 1, 2018, before deciding to reverse the policy entirely.

But the ban on transgender people in the military was repeatedly challenged in court, leading to an updated policy that also contained major restrictions on transgender service and which was also suspended because of its similarity to the original measure.

Transgender troops have been serving openly since January 1, 2018, but the government appealed and asked the Supreme Court to hear the case, requesting that it suspend the rulings of the lower courts.

Otherwise, "the nationwide injunction would... remain in place for at least another year and likely well into 2020 -- a period too long for the military to be forced to maintain a policy that it has determined, in its professional judgment, to be contrary to the nation's interests," the Trump administration argued.

The number of transgender troops among America's approximately 1.3 million active duty service members is fairly small, with estimates topping out at 15,000.