When President Trump speaks at the Values Voter Summit dinner in Washington on Saturday evening, he will be addressing a core constituency that helped him win the White House.

But as he presents a Cost of Discipleship Award to Andrew Brunson, the pastor whose 24-month detention in Turkey became a religious freedom cause célèbre, he will inadvertently highlight a growing source of anger for his audience of evangelical Christians.

Evangelicals are emerging as the most vocal critics of his decision to stand down U.S. forces in northern Syria, triggering dire warnings that Turkey’s incursion into the region threatens not just America’s Kurdish allies but vulnerable Christian communities.

The irony of honoring Brunson as a victim of Turkish intolerance will not be lost on attendees.

“Part of his story involves the bad action of the Turkish government on religious freedom,” said Travis Weber, director of the center for religious liberty at Family Research Council, which organizes the summit.

“We all know how the president had to get involved in taking action to win his release," he said. "And this is the same Turkey we are now looking at with such concern.”

Turkish forces are pushing deeper into northeastern Syria after four days of a cross-border offensive against Kurdish fighters of the YPG, U.S. allies in the fight against the Islamic State.

Christians in the region say they fear the operation will go well beyond Turkey’s stated aims of protecting its territory from “terrorists” of YPG.

“It is very possible that the American withdrawal from the region will lead to the extinction of Christianity from the region,” is how Ashty Bahro, former director of the Evangelical Alliance of Kurdistan, in Iraq, described it to Christianity Today amid a slew of appeals to Washington to rethink.

“Will the target be only terrorism or ‘undesirable people’? Leaving the area without proper care will lead to another disaster.”

The region is currently under the control of the Syrian Democratic Forces, of which the YPG is the main fighting force. Christian leaders in the U.S. look to it as a model for the rest of the Middle East in protecting religious minorities.

Local Christians have always feared a Turkish incursion would represent an attempt to shift the region’s mix of minorities, just as it did in Afrin last year. There, thousands of Yazidis and Christians were among the displaced as Turkish forces drove Kurdish YPG fighters from the town.

Their local warnings have been picked up and amplified by allies of Trump, who say it is shortsighted to let down an ally and give up on a partner that chimed with his administration’s work on religious freedom.

“This is good religious freedom policy, it is a good model for us to support,” said Weber. “They are protective of Christian minorities and religious freedom in a very robust way compared to elsewhere. Any protection of Christians gives it a lot of support in the United States.”

Dropping that support risks undermining Trump’s close relationship with evangelicals, according to many of the movement’s most prominent voices.

Pat Robertson, founder of the Christian Broadcasting Network, said, “I believe … the president of the United States is in danger of losing the mandate of heaven if he permits this to happen.”

Or as Franklin Graham, son of Rev. Billy Graham, put it: "The Kurds are the ones who have been leading the fight against ISIS in Syria. Also pray for the Christians who the Kurds have been protecting. They could be annihilated."

Evangelical voters were part of the coalition of voters that propelled Trump to power. They have remained enthusiastic supporters of an administration that has nominated two conservative judges to the Supreme Court and presided over a rollback in abortion services around the country.

The latest Pew Research poll found 77% of white evangelical Protestants approved of Trump’s performance.

The question now is whether a life-and-death problem for the regions Christians could undermine that support, even after accusations of sexual assault and infidelity or profanity-laced political rallies have had little effect.

Weber said his supporters on Saturday would want to hear a clear restatement of his support for religious freedom.

“His record has been solid,” he said. “He has been fantastic on the life issue, great on judges, he has been very good on religion. But this seems like a departure from his record, and we are very concerned about it.”

They received some assurance on Friday, when Treasury Secretary Steven Mnuchin, announced that Trump had authorized officials to draft sanctions if Turkey's offensive went too far.

"These are very powerful sanctions. We hope we don't have to use them, but we can shut down the Turkish economy if we need to," Mnuchin said.