Turkey’s main opposition party on Wednesday urged President Recep Tayyip Erdogan — currently visiting Washington — to rebuff controversial letters his U.S. counterpart sent him last month and this week.

”I call on Erdogan: Tonight, don’t be part of a work that makes our nation’s head bow,” Engin Altay, deputy group chair of the Republican People’s Party (CHP), told reporters in parliament. “We know how to back you.”

Altay’s remarks came ahead of a meeting between Erdogan and U.S. President Donald Trump on Wednesday at the White House.

Read more: Turkey: Opposition urges presidential rebuff of Trump