Photo taken on July 14, 2020 shows the U.S. Supreme Court building in Washington, D.C., the United States. The United States carried out its first execution at the federal level on Tuesday, putting white supremacist and murderer Daniel Lewis Lee to death by lethal injection. (Xinhua/Liu Jie)

The United States carried out its first execution at the federal level on Tuesday, putting white supremacist and murderer Daniel Lewis Lee to death by lethal injection.

The execution was carried out using the powerful sedative pentobarbital early in the day at the Federal Correctional Institution in Terre Haute, Indiana.

Originally scheduled for 4 p.m. Eastern Time (2000 GMT) on Monday, the execution was delayed by some 16 hours due to a federal judge's order to block it, but a 5 against 4 vote by the US Supreme Court eventually let it and another three upcoming executions "proceed as planned".

US District Judge Tanya Chutkan in Washington, who sought to prevent the execution, said Lee and another two death row inmates whose executions were scheduled later this week -- as well as a fourth whose execution is scheduled for August -- can pursue their claims that the federal government's plan to use a single drug would cause severe pain and needless suffering.

The four death row inmates claimed that the use of barbiturate pentobarbital constituted "cruel and unusual punishments" as it would interfere with breathing, causing a feeling of drowning and asphyxiation.

The Justice Department subsequently appealed Chutkan's order to both the US Court of Appeals for the D.C. Circuit and the Supreme Court.

While the appeals court declined to get involved, the Supreme Court overruled Chutkan's order, saying in an unsigned opinion that "the plaintiffs in this case have not made the showing required to justify last-minute intervention by a Federal Court."

Lee was convicted in 1999 of killing firearms dealer William Mueller in Arkansas in 1996, as well as his wife Nancy Mueller and their 8-year-old daughter Sarah Powell.

The execution was the first at the federal level since March 18, 2003, when Louis Jones was executed for "kidnapping within special maritime/territorial jurisdiction resulting in death," according to the Federal Bureau of Prisons.

The Trump administration resumed capital punishments at the federal level in July 2019.