Turkish President Recep Tayyip Erdogan is in Washington today to meet with President Donald Trump at the White House amid an intense crisis between the two NATO allies.

Erdogan says he will press the US president on the extradition of the Pennsylvania-based cleric Fethullah Gulen, a request the United States has long rebuffed. And The Washington Post reported Tuesday that Trump sent a letter to Erdogan ahead of the meeting offering not to implement legally mandated sanctions on Turkey. He reportedly floated a $100 billion trade deal in the letter as well. In return, Trump wants Erdogan to adhere to an October agreement where Turkish troops would refrain from venturing further into northeast Syria beyond the border area they already control.

Why it matters: Trump’s proposed counteroffer could fan the flames in Congress. Already outraged by Turkey’s incursion into northeast Syria following Trump’s military withdrawal from the border, lawmakers have called on Trump to cancel the meeting. Sen. Jeanne Shaheen, D-N.H., has urged “congressional leadership to seek a full accounting” of today’s White House talks. 

Trump’s apparent desire to avoid sanctioning Turkey for buying the Russian S-400 missile defense system could be a particularly sore spot on Capitol Hill. Congress overwhelmingly passed a 2017 law sanctioning any country that “engages in a significant transaction” with Russia’s defense and intelligence sector. Turkey received the first S-400 in a July shipment despite US concerns that the system’s radar could be used to spy on US military hardware.