As Turkey’s incursion into northern Syria continues, President Donald Trump is set to meet with Turkish President Recep Tayyip Erdogan at the White House on Wednesday, and for the Trump administration, a top priority is pressuring Turkey to take necessary steps to rejoin the most expensive American weapons program in history.

Since Turkey launched its offensive in northern Syria against a U.S.-allied, Kurdish-led militia last month, reports have emerged accusing Turkish forces or their allies of summary executions, attacks on residential areas, and using white phosphorus munitions. According to the Wall Street Journal, American reconnaissance drones have witnessed evidence of Turkish-backed forces deliberately targeting civilians.

Despite these reports of gross human rights violations, the priority for the Trump administration seems to be pushing Erdogan to reject the Russian-made S-400 missile defense system, which it first acquired this past summer. Instead, the United States would like to see Turkey resume its purchasing and manufacturing role in the F-35 Joint Strike Fighter program — a massive multinational weapons program that has been a major boon to U.S. defense manufacturers.

The U.S. began taking steps to suspend Turkey from the program in July, after Turkey began receiving shipments of the S-400. Turkey was set to buy 100 F-35s, valued at roughly $94 million apiece, as well as host much of the international manufacturing base for components and spare parts. The Pentagon has said the cost of retooling the program to exclude Turkish manufacturers alone will likely exceed $500 million.

Officials in the Trump administration have repeatedly said they are monitoring reports of human rights violations in Syria, but they have stopped short of commenting on whether such reports should also affect Turkey’s future in the F-35 program, or Turkey’s role as a buyer of U.S. weapons.

In recent days, senior Trump administration officials have suggested that they would consider reversing the F-35 decision if Turkey got rid of the S-400 system.

Defense Secretary Mark Esper told reporters on Monday, “I’ve been very clear in my last meeting with [Turkish] Defense Minister Akar. In Brussels I said once again, ‘You can’t have the S-400 and continue with the F-35.’ And so it’s too much of  — I think — the threat to the F-35.”

Trump’s national security adviser Robert O’Brien has said the S-400 issue would be raised at the White House summit. “We’ve made that very clear to President Erdogan. There’s no place in NATO for the S-400,” O’Brien told CBS on Sunday. “There’s no place in NATO for significant Russian military purchases. That’s a message that the president will deliver to him very clearly when he’s here in Washington.”

On Capitol Hill, relations with Turkey have been in a tailspin since at least October, when Trump decided to relocate U.S. troops in northern Syria after a phone call with Erdogan, essentially giving the Turkish president a green light to invade Syria. Congress is currently considering multiple measures to sanction Turkey for its reported abuses in Syria. Lawmakers have argued that the Trump administration should have already sanctioned Turkey for its purchase of the S-400 under a 2017 law called the Countering America’s Adversaries Through Sanctions Act, but the Trump administration has been reluctant to do so.

Last month the House of Representatives passed a resolution formally recognizing the 1915 Armenian genocide, which has long been opposed by the Turkish government.

For arms control experts, Trump’s reluctance to close the door on arms sales to Turkey is reminiscent of its relationship with Saudi Arabia. Jeff Abramson, a senior fellow at the Arms Control Association, told The Intercept by phone that Trump’s desire to pursue the F-35 program is consistent with a pattern of willingness to sell weapons to authoritarian regimes.

“It is consistent with Trump’s approach to the international arms trade that he would like to continue to sell weapons to Turkey,” Abramson said. “He has not had many qualms about selling to repressive regimes in the past. So his reticence to suspend the F-35 program is consistent with his transactional approach to the arms trade, rather than one that properly considers human rights and longer-term security issues.”

The reason the Trump administration has drawn a red line on the S-400 is that, as a monitoring and missile defense system, its intelligence capabilities could give Russian military intelligence an insight into how the F-35 works.

Undersecretary of Defense for Acquisition and Sustainment Ellen Lord explained this rationale in a July press conference, stressing that the Trump administration’s decision was based on the suspicion the F-35 could be compromised.”Turkey cannot field a Russian intelligence collection platform in proximity to where the F-35 program makes, repairs, and houses the F-35,” Lord said. “Much of the F-35’s strength lies in its stealth capabilities, so the ability to detect those capabilities would jeopardize the long-term security of the F-35 program.”

Merve Tahiroglu, the Turkey program coordinator at the Project on Middle East Democracy, told The Intercept that Trump’s decision to relocate U.S. troops in Syria — an apparent green light for Turkey’s invasion of Syria — leaves him with very little leverage to influence what Turkey does.

“This is a broader problem with U.S. foreign policy towards Turkey that we’ve seen under the Trump administration. There hasn’t been a proactive policy that could prevent these actions before they happen – both with the S-400 and the Syrian incursion. Both of these are actions that Ankara has long threatened to do.”

Turkey has been pursuing a deeper defense-industrial relationship with Russia for years. The two countries initially signed a $2.5 billion deal for the S-400 systems in late 2017, and the sale had been in the works for over a year prior to that.

In addition to Turkey’s offensive in Syria, in recent years Erdogan has overseen a crackdown on dissent at home. Following a failed coup attempt in 2017, Erdogan arrested more than 100 generals and arrested more than 70,000 people on alleged links to terrorist groups, according to the Associated Press. Erdogan has also used emergency decrees to shutter independent media and detain journalists.

Tahiroglu told The Intercept that, ideally, U.S. foreign policy would address Turkey’s domestic crackdown as well, which she says has led Erdogan to believe he is emboldened when acting abroad.

“In an ideal world any U.S. administration discussing foreign policy with Erdogan would be discussing the repression and crackdown on dissent that have made Erdogan’s aggressive foreign policy possible,” Tahiroglu said. “That would be the ideal world, but given the Trump administration’s general approach to foreign policy and close relationship with Erdogan, I don’t see that happening.”