WASHINGTON ― Rex Tillerson, President-elect Donald Trump’s nominee for secretary of state, endangered Christians in Iraq in 2011, a top House Democrat argued in a Tuesday night letter.

The allegation is a serious one, given that many lawmakers ― including most Republicans ― frequently bemoan the plight of Christians in the Middle East.

Rep. Jan Schakowsky (D-Ill.) wants legislators on the Senate Foreign Relations Committee to press Tillerson on the issue in committee hearings on his confirmation this week. The former Exxon Mobil chief executive threatened the heartland of Iraqi Christians ― who are split among various groups, including Assyrians, Chaldeans and Syriacs ― when his company negotiated a 2011 oil deal, she wrote in a letter to the committee’s chair and ranking member.

“The number of Christians in Iraq has declined from 1.2 million residents in 2003 to less than 250,000 today,” Schakowsky wrote. “The deals Mr. Tillerson signed exacerbated an already perilous situation for those beleaguered communities. He helped further marginalize the Assyrian/Chaldean/Syriac Christians and embolden the territorial expansion into their ancestral homeland ― all with neither consent or input from nor compensation to the indigenous communities of the Nineveh Plain.”

She wants senators to ask Tillerson about his knowledge of the deal, whether he believes U.S. policy should protect such minorities and how he plans to shield these communities “from private companies and governments who put profit over human safety and security.”

Read the full letter here.

The oil executive’s 2011 agreement to develop six northern Iraqi oilfields has long been controversial because it undercut U.S. policy on Iraq. By signing a deal with officials in the country’s semi-autonomous Kurdistan region rather than the central Iraqi government, Exxon boosted the Kurds’ claim that they are stable enough to have their own separate country.

The Iraqi Kurds are trusted U.S. partners, but American experts worry that their region becoming independent could force the U.S. to pick between Kurdistan and Iraq, worsen ethnic and sectarian tensions in the area and leave the remainder of the country more vulnerable to Iranian dominance. American officials saw the oil company’s move as unhelpful and selfish. When he learned of the Exxon-Kurdistan deal in November 2011, James Jeffrey, then the U.S. ambassador to Iraq, “dropped a few F-bombs,” a former diplomat told Reuters.

Growing Kurdish power has caused unrest among Christians in northern Iraq. The U.S. Commission on International Religious Freedom has said the Kurdistan government and Kurdish parties’ militias have subjected Christians to “pervasive discrimination and marginalization,” and advocates for those Christians say the Kurds have continuously encroached on their lands, which lie in disputed territory claimed by both the Kurdish region and Iraq.

SAFIN HAMED via Getty Images Christians at a Good Friday mass in Iraqi Kurdistan in 2016. While Kurdish authorities have welcomed Christian refugees, they have tried to absorb Christian territories into their region.

Deals like the Exxon agreement provide international legitimacy to such expansion. One of the areas where the American company recognized the Kurdistan government’s claims and received development rights is around an ancient Christian town called Alqosh.

“That’s ground zero for Assyrian survival,” said Steve Oshana, the executive director of A Demand For Action, an advocacy group for Middle East Christians. “Here is a situation where, with the machinery of an American company, more Assyrian resources are being taken … what this action does is it says to our community and the world that our indigenous rights are secondary to the oil rights of everyone else.”

With Kurdistan’s rulers becoming increasingly authoritarian ― and using the fight against the militant Islamic State group to justify repression ― Christian organizing has been difficult. Kurdistan security forces blocked a Christian protest last year, according to Human Rights Watch, and Christians hoping to help fight ISIS have been pressured to work under Kurdish command.

Lawmakers have previously recognized Iraqi Christians as targets of genocide and directed U.S. agencies to support Christian self-determination, including by encouraging the creation of a province of Iraq separate from Kurdistan that would include traditionally Christian lands.

For advocates who have seen Republicans and the religious right as partners in those efforts, the new party leader’s selection of Tillerson is a striking development.

“We’re not trying to stop the confirmation,” Oshana said. “However, as he’s rapidly going into his role, this is our opportunity to remind Mr. Tillerson that the actions that he took as a CEO had serious ramifications in marginalizing Christians, which is a group Donald Trump has vowed to help.”

Frequently (and deceptively) describing Muslims as violent, intolerant fanatics, Trump presented himself on the campaign trail as a defender of Christians in the Middle East. He won votes among communities of Christian immigrants from Iraq, Syria, Lebanon and elsewhere.

The Trump camp recently reached out to Oshana for a briefing on Christian concerns about Tillerson, he told HuffPost.

(The transition team did not respond to a HuffPost request for comment.)

The activist expects that Tillerson will be advised to acknowledge the consequences of his actions before he takes office. Spokespeople for the foreign relations committee’s chair, Sen. Bob Corker (R-Tenn.), and its ranking member, Sen. Ben Cardin (D-Md.), did not respond to a HuffPost inquiry about whether the lawmakers would bring up the issue during the hearings, as Schakowsky urged.

“He’s somebody who has had an active role in marginalizing our communities. That’s something people have forgiven [of him] as a CEO, but as secretary of state, he has to live up to Trump’s promise,” Oshana said. “If [Trump] really cares about helping our people, then this is a slam dunk.”