Amr Nabil, AP
A boy watches the front of Mar Mina church, in Helwan, Cairo, Egypt, Friday, Dec. 29, 2017, where several people have been killed in a shootout outside the church. (AP Photo/Amr Nabil)

At the start of the recent holiday weekend, two shopkeepers, eight other civilians and one police officer were shot to death in a rampage in Cairo. All of them, with the possible exception of the police officer, appear to have been targeted for their Christian faith. Eight were killed as they worshipped in a Coptic Orthodox church.

Religious persecution, especially but not exclusively aimed at Christians, is at an all-time high worldwide, according to some accounts. A recently released study by a group called Aid to the Church in Need documented the appalling treatment of Christians in many parts of the world, noting that the faith is in jeopardy of extinction in places such as Aleppo, Syria, which once housed one of the largest Christian communities in the Middle East.

Significantly, the report indicts Western governments and the United Nations for failing to help.

The United States, with its constitutional guarantee of religious liberty and its admirable history of religious pluralism, ought to be leading the charge against these despicable acts. Long seen as a sanctuary for the religiously oppressed, the United States has the military might and political influence to pressure other countries to allow religious freedom. Instead, it has seemed indifferent.

We once leveled this criticism against the Obama administration, but the Trump administration has proven little different.

Nearly one year after Mr. Trump took the oath of office, the ambassadorship at-large for international religious freedom remains vacant. The troubling message this sends to the rest of the world cannot be ignored.

Last July, Trump nominated Republican Kansas Gov. Sam Brownback to the post. As a senator in the 1990s, he was instrumental in passing the International Religious Freedom Act, which mandates an annual report on religious freedom abroad and requires the federal government to take action against international violators of religious liberty. President Clinton signed the act into law in 1998.

But Senate Democrats have blocked Brownback’s nomination over concerns about how, as governor, he revoked an executive order prohibiting discrimination against LGBT state government workers.

That action left the president with the option of either re-nominating Brownback or finding a different nominee more acceptable to Democrats. Instead, he has done neither, and the post has remained vacant.

The president should propose a confirmable nominee, and he ought to make this a priority for the new year.

The International Religious Freedom Act is bold in its declaration that “the right to freedom of religion undergirds the very origin and existence of the United States.” It also condemns the persecution of nonbelievers under regimes that enforce religious laws.

It states that U.S. policy is “to condemn violations of religious freedom, and to promote, and to assist other governments in the promotion of, the fundamental right to freedom of religion.”

That promotion requires an ambassador at-large for international religious freedom. Beyond that, it requires an administration willing to use that ambassador as a focal point of its diplomatic relations with foreign nations. Since 1998, no administration has properly done this.

But the first step is to nominate and confirm an ambassador. In a world where religious persecution is growing with impunity, the United States cannot afford to abdicate its unique responsibility to stem the tide.