US President Barack Obama told Iraqi Prime Minister Haider al-Abadi late on Wednesday that Turkey should withdraw from Iraq any military forces that have not been authorized by the Iraqi government in the latest call to urge Ankara to end the dispute with Baghdad.

In a phone call to the Iraqi prime minister, Obama and Abadi discussed their “mutual concern” over Saudi Arabia’s execution of Shiite cleric Nimr al-Nimr and the attacks on Saudi Arabia’s embassy in Iran, the White House said.

“They agreed on the need for all regional parties to demonstrate restraint, avoid provocative rhetoric or behavior, and avoid a worsening of sectarian tensions,” the White House said in a statement. “They agreed on the importance that all parties maintain diplomatic engagement and dialogue.”

Obama also spoke about the Turkey-Iraq rift over Turkish military presence in northern Iraq and called again for the withdrawal of all unauthorized Turkish forces.

For Washington, the dispute has the potential to hamper US efforts to assemble an alliance of groups in Iraq and neighboring countries in the fight against the Islamic State in Iraq and the Levant (ISIL) before an anticipated offensive to recapture Mosul, Iraq’s second largest city.