Turkey's President Recep Tayyip Erdogan delivers a speech Monday, a day after claiming victory in a referendum. The fairness of the vote has been challenged by the opposition and international observers. (Burhan Ozbilici/AP)

President Trump plans to meet next month with Turkish President Recep Tayyip Erdogan, according to Turkish and U.S. officials, just weeks after Erdogan claimed victory in a referendum that vastly increased his powers and has been questioned by the opposition and international observers.

Turkish Foreign Minister Mevlut Cavusoglu said Wednesday that the two leaders would sit down together before a NATO summit scheduled for May 29-30 in Brussels. A senior U.S. official confirmed that the meeting was “likely to occur.” The official spoke on the condition of anonymity prior to an announcement.

Trump telephoned Erdogan on Monday to “congratulate” him on “his referendum victory” and to discuss last week’s U.S. cruise missile strike on Syria and cooperation in the campaign there against the Islamic State, a White House statement said. The statement made no mention of widespread international concerns, including by the State Department, about the erosion of democratic institutions under the referendum and allegations of human rights violations leading up to it.

A State Department statement on the referendum cited “observed irregularities on voting day and an uneven playing field during the difficult campaign period, which took place during a state of emergency.”

“We look to the government of Turkey to protect the fundamental rights and freedoms of all its citizens,” the statement said.